Physics and Astronomy › Condensed Matter Physics

GaN-based semiconductor devices and materials

Works Count: 110073

Wikipedia

Description

This cluster of papers focuses on the first-principles calculations, properties, and applications of III-nitride semiconductors, particularly Gallium Nitride (GaN) and its alloys. It covers topics such as defects and impurities, band parameters, high-power light-emitting diodes (LEDs), AlGaN/GaN HEMTs, nanowires, UV LEDs, and their applications in solid-state lighting.

Keywords

III-Nitrides; Semiconductors; Light-Emitting Diodes; GaN; AlGaN/GaN HEMTs; Defects and Impurities; Solid-State Lighting; Nanowires; UV LEDs; Band Parameters

Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes

2000-08-01

Patrick Waltereit , O. Brandt , A. Trampert +5 more

Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting Diodes

1995-10-01

Shuji Nakamura , Masayuki Senoh , Naruhito Iwasa +3 more

Superbright green InGaN single quantum well (SQW) structure light-emitting diodes (LEDs) with a luminous intensity of 12 cd were fabricated. The luminous intensity of these green InGaN SQW LEDs (12 … Superbright green InGaN single quantum well (SQW) structure light-emitting diodes (LEDs) with a luminous intensity of 12 cd were fabricated. The luminous intensity of these green InGaN SQW LEDs (12 cd) was about 100 times higher than that of conventional green GaP LEDs (0.1 cd). The output power, the external quantum efficiency, the peak wavelength and the full width at half-maximum of green SQW LEDs were 3 mW, 6.3%, 520 nm and 30 nm, respectively, at a forward current of 20 mA. The p-AlGaN/InGaN/n-GaN structure of green InGaN SQW LEDs were grown by metalorganic chemical vapor deposition on sapphire subsutrates.

GaN-Based RF Power Devices and Amplifiers

2008-01-16

Umesh K. Mishra , Likun Shen , T.E. Kazior +1 more

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The rapid development of the RF power electronics requires the introduction of wide bandgap material due to its potential in high output power density, high operation voltage … <para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The rapid development of the RF power electronics requires the introduction of wide bandgap material due to its potential in high output power density, high operation voltage and high input impedance. GaN-based RF power devices have made substantial progresses in the last decade. This paper attempts to review the latest developments of the GaN HEMT technologies, including material growth, processing technologies, device epitaxial structures and MMIC designs, to achieve the state-of-the-art microwave and millimeter-wave performance. The reliability and manufacturing challenges are also discussed. </para>

Gallium vacancies and the yellow luminescence in GaN

1996-07-22

Jörg Neugebauer , Chris G. Van de Walle

We have investigated native defects and native defect-impurity complexes as candidate sources for the yellow luminescence in GaN. Using state-of-the-art first-principles calculations, we find strong evidence that the Ga vacancy … We have investigated native defects and native defect-impurity complexes as candidate sources for the yellow luminescence in GaN. Using state-of-the-art first-principles calculations, we find strong evidence that the Ga vacancy (VGa) is responsible. The dependence of the VGa formation energy on Fermi level explains why the yellow luminescence is observed only in n-type GaN. The VGa defect level is a deep acceptor state, consistent with recent pressure experiments. Finally we show that the formation of VGa is enhanced by the creation of complexes between VGa and donor impurities.

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Large-band-gap SiC, III-V nitride, and II-VI ZnSe-based semiconductor device technologies

1994-08-01

H. Morkoç̌ , S. Strite , Guangjun Gao +3 more

In the past several years, research in each of the wide-band-gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The … In the past several years, research in each of the wide-band-gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The merits of each contender for high-temperature electronics and short-wavelength optical applications are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hostile environments, and also make them attractive for high-power operation. The present advanced stage of development of SiC substrates and metal-oxide-semiconductor technology makes SiC the leading contender for high-temperature and high-power applications if ohmic contacts and interface-state densities can be further improved. GaN, despite fundamentally superior electronic properties and better ohmic contact resistances, must overcome the lack of an ideal substrate material and a relatively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high-temperature performance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the green, blue, or ultraviolet (UV) spectra. Blue SiC light-emitting diodes (LEDs) have been on the market for several years, joined recently by UV and blue GaN-based LEDs. These products should find wide use in full color display and other technologies. Promising prototype UV photodetectors have been fabricated from both SiC and GaN. In laser development, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage threshold of ZnSe continues to limit practical laser applications, GaN appears poised to become the semiconductor of choice for short-wavelength lasers in optical memory and other applications. For further development of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC substrates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN-based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on addressing the short lifetimes of ZnSe-based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide-band-gap semiconductor systems have moved away from materials science toward the device arena, where their technological development can rapidly be brought to maturity.

Synthesis of Gallium Nitride Nanorods Through a Carbon Nanotube-Confined Reaction

1997-08-29

Wei‐Qiang Han , Shoushan Fan , Qunqing Li +1 more

Gallium nitride nanorods were prepared through a carbon nanotube–confined reaction. Ga 2 O vapor was reacted with NH 3 gas in the presence of carbon nanotubes to form wurtzite gallium … Gallium nitride nanorods were prepared through a carbon nanotube–confined reaction. Ga 2 O vapor was reacted with NH 3 gas in the presence of carbon nanotubes to form wurtzite gallium nitride nanorods. The nanorods have a diameter of 4 to 50 nanometers and a length of up to 25 micrometers. It is proposed that the carbon nanotube acts as a template to confine the reaction, which results in the gallium nitride nanorods having a diameter similar to that of the original nanotubes. The results suggest that it might be possible to synthesize other nitride nanorods through similar carbon nanotube–confined reactions.

Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening

2004-02-04

Tetsuo Fujii , Yan Gao , Rajat Sharma +3 more

Roughened surfaces of light-emitting diodes (LEDs) provide substantial improvement in light extraction efficiency. By using the laser-lift-off technique followed by an anisotropic etching process to roughen the surface, an n-side-up … Roughened surfaces of light-emitting diodes (LEDs) provide substantial improvement in light extraction efficiency. By using the laser-lift-off technique followed by an anisotropic etching process to roughen the surface, an n-side-up GaN-based LED with a hexagonal “conelike” surface has been fabricated. The enhancement of the LED output power depends on the surface conditions. The output power of an optimally roughened surface LED shows a twofold to threefold increase compared to that of an LED before surface roughening.

Semiconductor ultraviolet detectors

1996-05-15

Manijeh Razeghi , Antoni Rogalski

In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on … In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further considerations are restricted to modern semiconductor UV detectors, so the basic theory of photoconductive and photovoltaic detectors is presented in a uniform way convenient for various detector materials. Next, the current state of the art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to a new generation of UV detectors fabricated from wide band-gap semiconductors the most promising of which are diamond and AlGaN. The latest progress in development of AlGaN UV detectors is finally described in detail.

An aluminium nitride light-emitting diode with a wavelength of 210 nanometres

2006-05-01

Yoshitaka Taniyasu , Makoto Kasu , Toshiki Makimōto

Unusual properties of the fundamental band gap of InN

2002-05-27

Junqiao Wu , W. Walukiewicz , K. M. Yu +6 more

The optical properties of wurtzite-structured InN grown on sapphire substrates by molecular-beam epitaxy have been characterized by optical absorption, photoluminescence, and photomodulated reflectance techniques. These three characterization techniques show an … The optical properties of wurtzite-structured InN grown on sapphire substrates by molecular-beam epitaxy have been characterized by optical absorption, photoluminescence, and photomodulated reflectance techniques. These three characterization techniques show an energy gap for InN between 0.7 and 0.8 eV, much lower than the commonly accepted value of 1.9 eV. The photoluminescence peak energy is found to be sensitive to the free-electron concentration of the sample. The peak energy exhibits very weak hydrostatic pressure dependence, and a small, anomalous blueshift with increasing temperature.

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Luminescence properties of defects in GaN

2005-03-15

M. A. Reshchikov , H. Morkoç̌

Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, … Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The point defects include native isolated defects (vacancies, interstitial, and antisites), intentional or unintentional impurities, as well as complexes involving different combinations of the isolated defects. Further improvements in device performance and longevity hinge on an in-depth understanding of point defects and their reduction. In this review a comprehensive and critical analysis of point defects in GaN, particularly their manifestation in luminescence, is presented. In addition to a comprehensive analysis of native point defects, the signatures of intentionally and unintentionally introduced impurities are addressed. The review discusses in detail the characteristics and the origin of the major luminescence bands including the ultraviolet, blue, green, yellow, and red bands in undoped GaN. The effects of important group-II impurities, such as Zn and Mg on the photoluminescence of GaN, are treated in detail. Similarly, but to a lesser extent, the effects of other impurities, such as C, Si, H, O, Be, Mn, Cd, etc., on the luminescence properties of GaN are also reviewed. Further, atypical luminescence lines which are tentatively attributed to the surface and structural defects are discussed. The effect of surfaces and surface preparation, particularly wet and dry etching, exposure to UV light in vacuum or controlled gas ambient, annealing, and ion implantation on the characteristics of the defect-related emissions is described.

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Auger recombination in InGaN measured by photoluminescence

2007-10-01

Yinchu Shen , Gerd Mueller , Satoshi Watanabe +3 more

The Auger recombination coefficient in quasi-bulk InxGa1−xN (x∼9%–15%) layers grown on GaN (0001) is measured by a photoluminescence technique. The samples vary in InN composition, thickness, and threading dislocation density. … The Auger recombination coefficient in quasi-bulk InxGa1−xN (x∼9%–15%) layers grown on GaN (0001) is measured by a photoluminescence technique. The samples vary in InN composition, thickness, and threading dislocation density. Throughout this sample set, the measured Auger coefficient ranges from 1.4×10−30to2.0×10−30cm6s−1. The authors argue that an Auger coefficient of this magnitude, combined with the high carrier densities reached in blue and green InGaN∕GaN (0001) quantum well light-emitting diodes (LEDs), is the reason why the maximum external quantum efficiency in these devices is observed at very low current densities. Thus, Auger recombination is the primary nonradiative path for carriers at typical LED operating currents and is the reason behind the drop in efficiency with increasing current even under room-temperature (short-pulsed, low-duty-factor) injection conditions.

Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer

1986-02-03

Hiroshi Amano , Nobuhiko Sawaki , Isamu Akasaki +1 more

Atmospheric pressure metalorganic vapor phase epitaxial growth and characterization of high quality GaN on sapphire (0001) substrates are reported. Using AlN buffer layers, GaN thin films with optically flat surfaces … Atmospheric pressure metalorganic vapor phase epitaxial growth and characterization of high quality GaN on sapphire (0001) substrates are reported. Using AlN buffer layers, GaN thin films with optically flat surfaces free from cracks are successfully grown. The narrowest x-ray rocking curve from the (0006) plane is 2.70′ and from the (202̄4) plane is 1.86′. Photoluminescence spectra show strong near band edge emission. The growth condition dependence of crystalline quality is also studied.

Wide-bandgap semiconductor ultraviolet photodetectors

2003-03-04

E. Monroy , F Omn s , F. Calle

Industries such as the automotive, aerospace or military, as well as environmental and biological research have promoted the development of ultraviolet (UV) photodetectors capable of operating at high temperatures and … Industries such as the automotive, aerospace or military, as well as environmental and biological research have promoted the development of ultraviolet (UV) photodetectors capable of operating at high temperatures and in hostile environments. UV-enhanced Si photodiodes are hence giving way to a new generation of UV detectors fabricated from wide-bandgap semiconductors, such as SiC, diamond, III-nitrides, ZnS, ZnO, or ZnSe. This paper provides a general review of latest progresses in wide-bandgap semiconductor photodetectors.

Quantum-Confined Stark Effect due to Piezoelectric Fields in GaInN Strained Quantum Wells

1997-04-01

Tetsuya Takeuchi , Shigetoshi Sota , Maki Katsuragawa +4 more

We have studied the influence of piezoelectric fields on luminescence properties of GaInN strained quantum wells. Our calculation suggests that an electric field of 1.08 MV/cm is induced by the … We have studied the influence of piezoelectric fields on luminescence properties of GaInN strained quantum wells. Our calculation suggests that an electric field of 1.08 MV/cm is induced by the piezoelectric effect in strained Ga 0.87 In 0.13 N grown on GaN. The photoluminescence peak energy of the Ga 0.87 In 0.13 N strained quantum wells showed blue shift with increasing excitation intensity. Moreover, the well-width dependence of its luminescence peak energy was well explained when the piezoelectric fields were taken into account. These results clearly showed that the piezoelectric field induced the quantum-confined Stark effect.

First-principles calculations for defects and impurities: Applications to III-nitrides

2004-03-25

Chris G. Van de Walle , Jörg Neugebauer

First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we … First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be attributed to nitrogen vacancies, but is due to unintentional incorporation of donor impurities. Native point defects may play a role in compensation and in phenomena such as the yellow luminescence, which can be attributed to gallium vacancies. In the section on impurities, specific attention will be focused on dopants. Oxygen, which is commonly present as a contaminant, is a shallow donor in GaN but becomes a deep level in AlGaN due to a DX transition. Magnesium is almost universally used as the p-type dopant, but hole concentrations are still limited. Reasons for this behavior are discussed, and alternative acceptors are examined. Hydrogen plays an important role in p-type GaN, and the mechanisms that underlie its behavior are explained. Incorporating hydrogen along with acceptors is an example of codoping; a critical discussion of codoping is presented. Most of the information available to date for defects and impurities in nitrides has been generated for GaN, but we will also discuss AlN and InN where appropriate. We conclude by summarizing the main points and looking towards the future.

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Band parameters for nitrogen-containing semiconductors

2003-09-15

I. Vurgaftman , J. R. Meyer

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” … We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature and alloy-composition dependences are also recommended wherever they are available. The “band anticrossing” model is employed to parameterize the fundamental band gap and conduction band properties of the dilute nitride materials.

Nitride-based semiconductors for blue and green light-emitting devices

1997-03-01

F. A. Ponce , D. P. Bour

Band Anticrossing in GaInNAs Alloys

1999-02-08

W. Shan , W. Walukiewicz , Joel W. Ager +5 more

We present evidence for a strong interaction between the conduction band and a narrow resonant band formed by nitrogen states in $\mathrm{Ga}{}_{1\ensuremath{-}x}\mathrm{In}{}_{x}\mathrm{N}{}_{y}\mathrm{As}{}_{1\ensuremath{-}y}$ alloys. The interaction leads to a splitting of … We present evidence for a strong interaction between the conduction band and a narrow resonant band formed by nitrogen states in $\mathrm{Ga}{}_{1\ensuremath{-}x}\mathrm{In}{}_{x}\mathrm{N}{}_{y}\mathrm{As}{}_{1\ensuremath{-}y}$ alloys. The interaction leads to a splitting of the conduction band into two subbands and a reduction of the fundamental band gap. An anticrossing of the extended states of the conduction band of the $\mathrm{Ga}{}_{1\ensuremath{-}x}\mathrm{In}{}_{x}\mathrm{As}$ matrix and the localized nitrogen resonant states is used to model the interaction. Optical transitions associated with the energy minima of the two subbands and the characteristic anticrossing behavior of the transitions under applied hydrostatic pressure have been unambiguously observed using photomodulation spectroscopy. The experimental results are in excellent quantitative agreement with the model.

Growth and applications of Group III-nitrides

1998-10-21

O. Ambacher

Recent research results pertaining to InN, GaN and AlN are reviewed, focusing on the different growth techniques of Group III-nitride crystals and epitaxial films, heterostructures and devices. The chemical and … Recent research results pertaining to InN, GaN and AlN are reviewed, focusing on the different growth techniques of Group III-nitride crystals and epitaxial films, heterostructures and devices. The chemical and thermal stability of epitaxial nitride films is discussed in relation to the problems of deposition processes and the advantages for applications in high-power and high-temperature devices. The development of growth methods like metalorganic chemical vapour deposition and plasma-induced molecular beam epitaxy has resulted in remarkable improvements in the structural, optical and electrical properties. New developments in precursor chemistry, plasma-based nitrogen sources, substrates, the growth of nucleation layers and selective growth are covered. Deposition conditions and methods used to grow alloys for optical bandgap and lattice engineering are introduced. The review is concluded with a description of recent Group III-nitride semiconductor devices such as bright blue and white light-emitting diodes, the first blue-emitting laser, high-power transistors, and a discussion of further applications in surface acoustic wave devices and sensors.

Origin of efficiency droop in GaN-based light-emitting diodes

2007-10-29

Minho Kim , M. Schubert , Qi Dai +4 more

The efficiency droop in GaInN∕GaN multiple-quantum well (MQW) light-emitting diodes is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the … The efficiency droop in GaInN∕GaN multiple-quantum well (MQW) light-emitting diodes is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the photoluminescence output as a function of excitation power shows no droop, indicating that the droop is not related to MQW efficiency but rather to the recombination of carriers outside the MQW region. Simulations show that polarization fields in the MQW and electron blocking layer enable the escape of electrons from the MQW region and thus are the physical origin of the droop. It is shown that through the use of proper quaternary AlGaInN compositions, polarization effects are reduced, thereby minimizing droop and improving efficiency.

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InGaN-Based Multi-Quantum-Well-Structure Laser Diodes

1996-01-01

Shuji Nakamura , Masayuki Senoh , Shin‐ichi Nagahama +5 more

InGaN multi-quantum-well (MQW) structure laser diodes (LDs) fabricated from III-V nitride materials were grown by metalorganic chemical vapor deposition on sapphire substrates. The mirror facet for a laser cavity was … InGaN multi-quantum-well (MQW) structure laser diodes (LDs) fabricated from III-V nitride materials were grown by metalorganic chemical vapor deposition on sapphire substrates. The mirror facet for a laser cavity was formed by etching of III-V nitride films without cleaving. As an active layer, the InGaN MQW structure was used. The InGaN MQW LDs produced 215 mW at a forward current of 2.3 A, with a sharp peak of light output at 417 nm that had a full width at half-maximum of 1.6 nm under the pulsed current injection at room temperature. The laser threshold current density was 4 kA/cm 2 . The emission wavelength is the shortest one ever generated by a semiconductor laser diode.

III–nitrides: Growth, characterization, and properties

2000-02-01

S.C. Jain , M. Willander , J. Narayan +1 more

During the last few years the developments in the field of III–nitrides have been spectacular. High quality epitaxial layers can now be grown by MOVPE. Recently good quality epilayers have … During the last few years the developments in the field of III–nitrides have been spectacular. High quality epitaxial layers can now be grown by MOVPE. Recently good quality epilayers have also been grown by MBE. Considerable work has been done on dislocations, strain, and critical thickness of GaN grown on different substrates. Splitting of valence band by crystal field and by spin-orbit interaction has been calculated and measured. The measured values agree with the calculated values. Effects of strain on the splitting of the valence band and on the optical properties have been studied in detail. Values of band offsets at the heterointerface between several pairs of different nitrides have been determined. Extensive work has been done on the optical and electrical properties. Near band-edge spectra have been measured over a wide range of temperatures. Free and bound exciton peaks have been resolved. Valence band structure has been determined using the PL spectra and compared with the theoretically calculated spectra. Strain and its effect on the optical properties of the III–nitride layers have been studied both theoretically and experimentally. Both n and p conductivity have been achieved. InGaN quantum wells with GaN and AlGaN barriers and cladding layers have been investigated. PL of the quantum wells is affected by confinement effects, band filling, quantum confined Stark effect, and strain. This work has led to the fabrication of advanced optoelectronic and electronic devices. The light-emitting decodes emitting in the blue and green regions of the spectrum have been commercialized. The work leading to these developments is reviewed in this article. The device processing methods and actual devices are not discussed.

Deep Ultraviolet Light-Emitting Hexagonal Boron Nitride Synthesized at Atmospheric Pressure

2007-08-16

Yoichi Kubota , Kenji Watanabe , Osamu Tsuda +1 more

Materials emitting light in the deep ultraviolet region around 200 nanometers are essential in a wide-range of applications, such as information storage technology, environmental protection, and medical treatment. Hexagonal boron … Materials emitting light in the deep ultraviolet region around 200 nanometers are essential in a wide-range of applications, such as information storage technology, environmental protection, and medical treatment. Hexagonal boron nitride (hBN), which was recently found to be a promising deep ultraviolet light emitter, has traditionally been synthesized under high pressure and at high temperature. We successfully synthesized high-purity hBN crystals at atmospheric pressure by using a nickel-molybdenum solvent. The obtained hBN crystals emitted intense 215-nanometer luminescence at room temperature. This study demonstrates an easier way to grow high-quality hBN crystals, through their liquid-phase deposition on a substrate at atmospheric pressure.

Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes

1994-03-28

Shuji Nakamura , Takashi Mukai , Masayuki Senoh

Candela-class high-brightness InGaN/AlGaN double-heterostructure (DH) blue-light-emitting diodes (LEDs) with the luminous intensity over 1 cd were fabricated. As an active layer, a Zn-doped InGaN layer was used for the DH … Candela-class high-brightness InGaN/AlGaN double-heterostructure (DH) blue-light-emitting diodes (LEDs) with the luminous intensity over 1 cd were fabricated. As an active layer, a Zn-doped InGaN layer was used for the DH LEDs. The typical output power was 1500 μW and the external quantum efficiency was as high as 2.7% at a forward current of 20 mA at room temperature. The peak wavelength and the full width at half-maximum of the electroluminescence were 450 and 70 nm, respectively. This value of luminous intensity was the highest ever reported for blue LEDs.

GaN, AlN, and InN: A review

1992-07-01

S. Strite , H. Morkoç

The status of research on both wurtzite and zinc-blende GaN, AlN, and InN and their alloys is reviewed including exciting recent results. Attention is paid to the crystal growth techniques, … The status of research on both wurtzite and zinc-blende GaN, AlN, and InN and their alloys is reviewed including exciting recent results. Attention is paid to the crystal growth techniques, structural, optical, and electrical properties of GaN, AlN, InN, and their alloys. The various theoretical results for each material are summarized. We also describe the performance of several device structures which have been demonstrated in these materials. Near-term goals and critical areas in need of further research in the III–V nitride material system are identified.

P-Type Conduction in Mg-Doped GaN Treated with Low-Energy Electron Beam Irradiation (LEEBI)

1989-12-01

Hiroshi Amano , M. Kito , Kazumasa Hiramatsu +1 more

Distinct p-type conduction is realized with Mg-doped GaN by the low-energy electron-beam irradiation (LEEBI) treatment, and the properties of the GaN p-n junction LED are reported for the first time. … Distinct p-type conduction is realized with Mg-doped GaN by the low-energy electron-beam irradiation (LEEBI) treatment, and the properties of the GaN p-n junction LED are reported for the first time. It was found that the LEEBI treatment drastically lowers the resistivity and remarkably enhances the PL efficiency of MOVPE-grown Mg-doped GaN. The Hall effect measurement of this Mg-doped GaN treated with LEEBI at room temperature showed that the hole concentration is ∼2·10 16 cm -3 , the hole mobility is ∼8 cm 2 /V·s and the resistivity is ∼35 Ω·cm. The p-n junction LED using Mg-doped GaN treated with LEEBI as the p-type material showed strong near-band-edge emission due to the hole injection from the p-layer to the n-layer at room temperature.

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Spontaneous emission of localized excitons in InGaN single and multiquantum well structures

1996-12-30

Shigefusa F. Chichibu , T. Azuhata , T. Sota +1 more

Emission mechanisms of InGaN single quantum well blue and green light emitting diodes and multiquantum well structures were investigated by means of modulation spectroscopy. Their static electroluminescence (EL) peak was … Emission mechanisms of InGaN single quantum well blue and green light emitting diodes and multiquantum well structures were investigated by means of modulation spectroscopy. Their static electroluminescence (EL) peak was assigned to the recombination of excitons localized at certain potential minima in the quantum well. The blueshift of the EL peak caused by the increase of the driving current was explained by combined effects of the quantum-confinement Stark effect and band filling of the localized states by excitons.

Single-crystal gallium nitride nanotubes

2003-04-01

Joshua E. Goldberger , Rongrui He , Yanfeng Zhang +4 more

High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well Structures

1995-07-01

Shuji Nakamura , Masayuki Senoh , Naruhito Iwasa +1 more

High-brightness blue, green and yellow light-emitting diodes (LEDs) with quantum well structures based on III-V nitrides were grown by metalorganic chemical vapor deposition on sapphire substrates. The typical green LEDs … High-brightness blue, green and yellow light-emitting diodes (LEDs) with quantum well structures based on III-V nitrides were grown by metalorganic chemical vapor deposition on sapphire substrates. The typical green LEDs had a peak wavelength of 525 nm and full width at half-maximum (FWHM) of 45 nm. The output power, the external quantum efficiency and the luminous intensity of green LEDs at a forward current of 20 mA were 1 mW, 2.1% and 4 cd, respectively. The luminous intensity of green LEDs (4 cd) was about 40 times higher than that of conventional green GaP LEDs (0.1 cd). Typical yellow LEDs had a peak wavelength of 590 nm and FWHM of 90 nm. The output power of yellow LEDs was 0.5 mW at 20 mA. When the emission wavelength of III-V nitride LEDs with quantum well structures increased from the region of blue to yellow, the output power decreased dramatically.

GaN Growth Using GaN Buffer Layer

1991-10-01

Shuji Nakamura Shuji Nakamura

High-quality gallium nitride (GaN) film was obtained for the first time using a GaN buffer layer on a sapphire substrate. An optically flat and smooth surface was obtained over a … High-quality gallium nitride (GaN) film was obtained for the first time using a GaN buffer layer on a sapphire substrate. An optically flat and smooth surface was obtained over a two-inch sapphire substrate. Hall measurement was performed on GaN films grown with a GaN buffer layer as a function of the thickness of the GaN buffer layer. For the GaN film grown with a 200 Å-GaN buffer layer, the carrier concentration and Hall mobility were 4×10 16 /cm 3 and 600 cm 2 /V·s, respectively, at room temperature. The values became 8×10 15 /cm 3 and 1500 cm 2 /V·s at 77 K, respectively. These values of Hall mobility are the highest ever reported for GaN films. The Hall measurement shows that the optimum thickness of the GaN buffer layer is around 200 Å.

GaN: Processing, defects, and devices

1999-07-01

S. J. Pearton , J.C. Zolper , R. J. Shul +1 more

The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the … The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Thermal Annealing Effects on P-Type Mg-Doped GaN Films

1992-02-01

Shuji Nakamura , Takashi Mukai , Masayuki Senoh +1 more

Low-resistivity p-type GaN films were obtained by N 2 -ambient thermal annealing at temperatures above 700°C for the first time. Before thermal annealing, the resistivity of Mg-doped GaN films was … Low-resistivity p-type GaN films were obtained by N 2 -ambient thermal annealing at temperatures above 700°C for the first time. Before thermal annealing, the resistivity of Mg-doped GaN films was approximately 1×10 6 Ω·cm. After thermal annealing at temperatures above 700°C, the resistivity, hole carrier concentration and hole mobility became 2 Ω·cm, 3×10 17 /cm 3 and 10 cm 2 /V·s, respectively. In photoluminescence measurements, the intensity of 750-nm deep-level emissions (DL emissions) sharply decreased upon thermal annealing at temperatures above 700°C, as did the change in resistivity, and 450-nm blue emissions showed maximum intensity at approximately 700°C of thermal annealing.

Prospects for LED lighting

2009-03-31

Siddha Pimputkar , James S. Speck , Steven P. DenBaars +1 more

Two dimensional electron gases induced by spontaneous and piezoelectric polarization in undoped and doped AlGaN/GaN heterostructures

2000-01-01

O. Ambacher , B. E. Foutz , J. Smart +7 more

Two dimensional electron gases in AlxGa1−xN/GaN based heterostructures, suitable for high electron mobility transistors, are induced by strong polarization effects. The sheet carrier concentration and the confinement of the two … Two dimensional electron gases in AlxGa1−xN/GaN based heterostructures, suitable for high electron mobility transistors, are induced by strong polarization effects. The sheet carrier concentration and the confinement of the two dimensional electron gases located close to the AlGaN/GaN interface are sensitive to a large number of different physical properties such as polarity, alloy composition, strain, thickness, and doping of the AlGaN barrier. We have investigated these physical properties for undoped and silicon doped transistor structures by a combination of high resolution x-ray diffraction, atomic force microscopy, Hall effect, and capacitance–voltage profiling measurements. The polarization induced sheet charge bound at the AlGaN/GaN interfaces was calculated from different sets of piezoelectric constants available in the literature. The sheet carrier concentration induced by polarization charges was determined self-consistently from a coupled Schrödinger and Poisson equation solver for pseudomorphically and partially relaxed barriers with different alloy compositions. By comparison of theoretical and experimental results, we demonstrate that the formation of two dimensional electron gases in undoped and doped AlGaN/GaN structures rely both on piezoelectric and spontaneous polarization induced effects. In addition, mechanisms reducing the sheet carrier concentrations like nonabrupt interfaces, dislocations, and the possible influence of surface states on the two dimensional electron gases will be discussed briefly.

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Single gallium nitride nanowire lasers

2002-09-15

Justin C. Johnson , Heon‐Jin Choi , Kelly P. Knutsen +3 more

THE PREPARATION AND PROPERTIES OF VAPOR-DEPOSITED SINGLE-CRYSTAL-LINE GaN

1969-11-15

H. Paul Maruska , J. J. Tietjen

Single-crystalline, colorless, GaN has been prepared by a vapor-phase growth technique previously used to prepare GaAs, GaP, and GaSb. These crystals are the first reported speciments of GaN suitable for … Single-crystalline, colorless, GaN has been prepared by a vapor-phase growth technique previously used to prepare GaAs, GaP, and GaSb. These crystals are the first reported speciments of GaN suitable for good electrical and optical evaluation of this compound. It has been determined that GaN has a direct energy bandgap of 3.39 eV, and that undoped crystals prepared by this method have a very high inherent electron concentration, typically above 1019/cm3, which is probably related to a high density of nitrogen vacancies. Conducting p-type specimens have been prepared using Ge as the dopant; but this result has been difficult to reproduce, and the samples have been electrically inhomogeneous.

The Roles of Structural Imperfections in InGaN-Based Blue Light-Emitting Diodes and Laser Diodes

1998-08-14

Shuji Nakamura

REVIEW High-efficiency light-emitting diodes emitting amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layer instead of a GaN active layer. The localized … REVIEW High-efficiency light-emitting diodes emitting amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layer instead of a GaN active layer. The localized energy states caused by In composition fluctuation in the InGaN active layer are related to the high efficiency of the InGaN-based emitting devices. The blue and green InGaN quantum-well structure light-emitting diodes with luminous efficiencies of 5 and 30 lumens per watt, respectively, can be made despite the large number of threading dislocations (1 × 10 8 to 1 × 10 12 cm −2 ). Epitaxially laterally overgrown GaN on sapphire reduces the number of threading dislocations originating from the interface of the GaN epilayer with the sapphire substrate. InGaN multi-quantum-well structure laser diodes formed on the GaN layer above the SiO 2 mask area can have a lifetime of more than 10,000 hours. Dislocations increase the threshold current density of the laser diodes.

Spontaneous polarization and piezoelectric constants of III-V nitrides

1997-10-15

Fabio Bernardini , Vincenzo Fiorentini , David Vanderbilt

The spontaneous polarization, dynamical Born charges, and piezoelectric constants of the III-V nitrides AlN, GaN, and InN are studied ab initio using the Berry-phase approach to polarization in solids. The … The spontaneous polarization, dynamical Born charges, and piezoelectric constants of the III-V nitrides AlN, GaN, and InN are studied ab initio using the Berry-phase approach to polarization in solids. The piezoelectric constants are found to be up to ten times larger than in conventional III-V and II-VI semiconductor compounds, and comparable to those of ZnO. Further properties at variance with those of conventional III-V compounds are the sign of the piezoelectric constants (positive as in II-VI compounds) and the very large spontaneous polarization.

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Direct-bandgap properties and evidence for ultraviolet lasing of hexagonal boron nitride single crystal

2004-05-23

Kenji Watanabe , Takashi Taniguchi , H. Kanda

The impact of surface states on the DC and RF characteristics of AlGaN/GaN HFETs

2001-03-01

R. Vetury , N.Q. Zhang , S. Keller +1 more

GaN based HFETs are of tremendous interest in applications requiring high power at microwave frequencies. Although excellent current-voltage (I-V) characteristics and record high output power densities at microwave frequencies have … GaN based HFETs are of tremendous interest in applications requiring high power at microwave frequencies. Although excellent current-voltage (I-V) characteristics and record high output power densities at microwave frequencies have been achieved, the origin of the 2DEG and the factors limiting the output power and reliability of the devices under high power operation remain uncertain. Drain current collapse has been the major obstacle in the development of reliable high power devices. We show that the cause of current collapse is a charging up of a second virtual gate, physically located in the gate drain access region. Due to the large bias voltages present on the device during a microwave power measurement, surface states in the vicinity of the gate trap electrons, thus acting as a negatively charged virtual gate. The maximum current available from a device during a microwave power measurement is limited by the discharging of this virtual gate. Passivated devices located adjacent to unpassivated devices on the same wafer show almost no current collapse, thus demonstrating that proper surface passivation prevents the formation of the virtual gate. The possible mechanisms by which a surface passivant reduces current collapse and the factors affecting reliability and stability of such a passivant are discussed.

Status and Future of High-Power Light-Emitting Diodes for Solid-State Lighting

2007-06-01

Michael R. Krames , O.B. Shchekin , Regina Mueller‐Mach +4 more

Status and future outlook of III-V compound semiconductor visible-spectrum light-emitting diodes (LEDs) are presented. Light extraction techniques are reviewed and extraction efficiencies are quantified in the 60%+ (AlGaInP) and ~80% … Status and future outlook of III-V compound semiconductor visible-spectrum light-emitting diodes (LEDs) are presented. Light extraction techniques are reviewed and extraction efficiencies are quantified in the 60%+ (AlGaInP) and ~80% (InGaN) regimes for state-of-the-art devices. The phosphor-based white LED concept is reviewed and recent performance discussed, showing that high-power white LEDs now approach the 100-lm/W regime. Devices employing multiple phosphors for "warm" white color temperatures (~3000-4000 K) and high color rendering (CRI>80), which provide properties critical for many illumination applications, are discussed. Recent developments in chip design, packaging, and high current performance lead to very high luminance devices (~50 Mcd/m 2 white at 1 A forward current in 1times1 mm 2 chip) that are suitable for application to automotive forward lighting. A prognosis for future LED performance levels is considered given further improvements in internal quantum efficiency, which to date lag achievements in light extraction efficiency for InGaN LEDs

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Illumination with solid state lighting technology

2002-01-01

D. A. Steigerwald , J Bhat , D. M. Collins +5 more

High-power light-emitting diodes (LEDs) have begun to differentiate themselves from their more common cousins the indicator LED. Today these LEDs are designed to generate 10-100 lm per LED with efficiencies … High-power light-emitting diodes (LEDs) have begun to differentiate themselves from their more common cousins the indicator LED. Today these LEDs are designed to generate 10-100 lm per LED with efficiencies that surpass incandescent and halogen bulbs. After a summary of the motivation for the development of the high-power LED and a look at the future markets, we describe the current state of high-power LED technology and the challenges that lay ahead for development of a true "solid state lamp." We demonstrate record performance and reliability for high-power colored and white LEDs and show results from the worlds first 100-plus lumen white LED lamp, the solid state equivalent of Thomas Edison's 20-W incandescent lightbulb approximately one century later.

Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures

1999-03-15

O. Ambacher , J. Smart , J. R. Shealy +7 more

Carrier concentration profiles of two-dimensional electron gases are investigated in wurtzite, Ga-face AlxGa1−xN/GaN/AlxGa1−xN and N-face GaN/AlxGa1−xN/GaN heterostructures used for the fabrication of field effect transistors. Analysis of the measured electron … Carrier concentration profiles of two-dimensional electron gases are investigated in wurtzite, Ga-face AlxGa1−xN/GaN/AlxGa1−xN and N-face GaN/AlxGa1−xN/GaN heterostructures used for the fabrication of field effect transistors. Analysis of the measured electron distributions in heterostructures with AlGaN barrier layers of different Al concentrations (0.15&lt;x&lt;0.5) and thickness between 20 and 65 nm demonstrate the important role of spontaneous and piezoelectric polarization on the carrier confinement at GaN/AlGaN and AlGaN/GaN interfaces. Characterization of the electrical properties of nominally undoped transistor structures reveals the presence of high sheet carrier concentrations, increasing from 6×1012 to 2×1013 cm−2 in the GaN channel with increasing Al-concentration from x=0.15 to 0.31. The observed high sheet carrier concentrations and strong confinement at specific interfaces of the N- and Ga-face pseudomorphic grown heterostructures can be explained as a consequence of interface charges induced by piezoelectric and spontaneous polarization effects.

AlGaN/GaN HEMTs-an overview of device operation and applications

2002-06-01

Umesh K. Mishra , P. Parikh , Yifeng Wu

Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, … Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor seems the most promising. This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems.

Surface-plasmon-enhanced light emitters based on InGaN quantum wells

2004-08-22

Koichi Okamoto , Isamu Niki , Alexander Shvartser +3 more

GaN-on-Si Power Technology: Devices and Applications

2017-02-27

Kevin J. Chen , Oliver D. Häberlen , Alex Lidow +4 more

In this paper, we present a comprehensive review and discussion of the state-of-the-art device technology and application development of GaN-on-Si power electronics. Several device technologies for realizing normally off operation … In this paper, we present a comprehensive review and discussion of the state-of-the-art device technology and application development of GaN-on-Si power electronics. Several device technologies for realizing normally off operation that is highly desirable for power switching applications are presented. In addition, the examples of circuit applications that can greatly benefit from the superior performance of GaN power devices are demonstrated. Comparison with other competing power device technology, such as Si superjunction-MOSFET and SiC MOSFET, is also presented and analyzed. Critical issues for commercialization of GaN-on-Si power devices are discussed with regard to cost, reliability, and ease of use.

The emergence and prospects of deep-ultraviolet light-emitting diode technologies

2019-03-22

Michael Kneissl , Tae‐Yeon Seong , Jung Han +1 more

Influence of mode polarization on the emission dynamics of Zinc-Oxide nanowire lasers coupled to planar aluminum substrates

2025-06-25

Daniel Repp , Devapriyo Mithun , Francesco Vitale +7 more | Optics Letters

High-performance AlN/GaN/AlGaN-MOSHEMTs on SiC wafer: scaling and gate material innovations for upcoming radar and communication systems

2025-06-25

Lavanya Repaka , J. Ajayan , Asisa Kumar Panigrahy +2 more | Journal of the Korean Physical Society

Temperature‐Dependent Transition in the Dominant Nonradiative Carrier Recombination Process in Ultrathin AlN/GaN/AlN‐Quantum Wells Studied by Phononic–Excitonic–Radiative Model

2025-06-24

Masaya Chizaki , Yoshihiro Ishitani | physica status solidi (b)

The analysis of the activation mechanism of the nonradiative electron–hole recombination (NRR) process is a crucial issue in improving the radiation efficiency of light‐emitting devices. This article shows the mechanism … The analysis of the activation mechanism of the nonradiative electron–hole recombination (NRR) process is a crucial issue in improving the radiation efficiency of light‐emitting devices. This article shows the mechanism determining the functional feature of the dependence of NRR rate in quantum wells (QWs) on temperature, taking an example of ultrathin AlN/GaN(one molecular layer)/AlN QW. An analysis is conducted by introducing exciton and free‐carrier NRR channels to the 2D phononic–excitonic–radiative model, including carrier injection, recombination, electron collisional, and phononic excitation and de‐excitation transfer of excitonic states. The exciton and free‐carrier NRR processes, the activation energy of the NRR process, and the exciton binding energy are the parameters of the dependence. It is found that the population distribution in the exciton system is a crucial factor for the dependence of the NRR rate on temperature. The experimentally observed almost constant or weak decrease in the NRR rate with increasing temperature in the vicinity of 300 K is attributed to the rate balance between exciton and free‐carrier processes. The reason for the nearly constant feature and faint decrease in the low‐temperature region remains covered; the energy‐dependent cross‐sectional feature of low‐velocity excitons and the nonthermal electron–lattice system are required to be studied.

Stability of p-GaN gate AlGaN/GaN HEMTs under static and dynamic drain stress

2025-06-24

Linfei Gao , Xiaohua Li , Wei He +7 more | Deleted Journal

Abstract In this article, we report the investigation into the stability of p-GaN gate high electron mobility transistors (HEMTs) with an internal integrated gate circuit that led to the design … Abstract In this article, we report the investigation into the stability of p-GaN gate high electron mobility transistors (HEMTs) with an internal integrated gate circuit that led to the design of a capacitance-based circuit to address threshold voltage shifts (Δ V TH ). Pulse I–V measurement revealed a notable positive gate V TH shift of 0.7 V as the drain voltage increased from 0 to 650 V, highlighting the impact of drain bias on V TH instability. Through the investigation of drain bias-induced V TH instability and the behavior of carriers being transported within the gate region, it was found that the maximum Δ V TH is 0.4 V when a 200-V drain bias is applied; after stress removal, Δ V TH diminishes gradually due to the discharge of capacitance, and holes enter the p-GaN layer to mitigate the depletion of holes. The integration of passive components and p-GaN gate HEMT circuits is suggested to address V TH instability in enhancement-mode HEMT devices. The reliability of power devices is essential for their acceptance in emerging applications.

Fabrication and characterization of AlGaInN/GaInN/GaN n-p-n heterojunction bipolar transistors with a p+-GaN contact layer

2025-06-24

Akira Mase , Masaya Takimoto , Ryotaro Inoue +3 more | Japanese Journal of Applied Physics

Abstract In this study, we fabricated and characterized AlGaInN/GaInN/GaN n-p-n heterojunction bipolar transistors (HBTs) with a selectively regrown p+-GaN layer for the base/metal contact on a free-standing GaN substrate by … Abstract In this study, we fabricated and characterized AlGaInN/GaInN/GaN n-p-n heterojunction bipolar transistors (HBTs) with a selectively regrown p+-GaN layer for the base/metal contact on a free-standing GaN substrate by metalorganic chemical vapor deposition. The use of the p+-GaN contact layer surely improved the base/metal electrical property and the base/emitter current injection, and thereby the fabricated HBTs exhibited good output DC characteristics. The maximum current density and the maximum current gain were estimated to be 2.0 A·cm-2 and 64, respectively.

Estimation of net acceptor activation ratio of channeled-implanted Mg from breakdown voltage analysis of vertical GaN p-n junction diodes with junction termination extension

2025-06-23

Kazuki Kitagawa , Tsutomu Uesugi , Masahiro Horita +2 more | Japanese Journal of Applied Physics

Abstract We fabricated vertical GaN p-n junction diodes (PNDs) with junction termination extension (JTE) structures by channeled implantation of Mg ions at four different dosages into n-type GaN homoepitaxial layers … Abstract We fabricated vertical GaN p-n junction diodes (PNDs) with junction termination extension (JTE) structures by channeled implantation of Mg ions at four different dosages into n-type GaN homoepitaxial layers and subsequent ultra-high-pressure activation annealing. The breakdown voltage (BV) of the fabricated PNDs increased with the dosage. By comparing the measured BV values with those obtained from TCAD simulations, we estimated the net acceptor activation ratio (net acceptor concentration/Mg concentration in the p-type JTE region). This ratio was estimated to range from 10 to 25%. Our method is useful for further optimization of the implantation and annealing conditions.

First-principles study of point defects in AlGaN: Insights into defect properties and growth optimization

2025-06-23

Liangbing Ge , Ran Tao , Dongguo Zhang +4 more | Computational Materials Science

Full-color monolithic InGaN micro-LEDs through tunnel junctions with true red emission

2025-06-23

Anda Cheng , You-Shiuan Chang , Zhongying Zhang +7 more | Optics Express

Full-color monolithic InGaN micro-LEDs can achieve the transfer of full-color subpixels through a single flip-chip bonding process, offering advantages such as simplified fabrication processes and reduced production costs for micro-LED … Full-color monolithic InGaN micro-LEDs can achieve the transfer of full-color subpixels through a single flip-chip bonding process, offering advantages such as simplified fabrication processes and reduced production costs for micro-LED display. In this paper, we demonstrate a structure that utilizes a pseudo-quantum well to achieve long-wavelength red emission, which is applied to full-color monolithic InGaN micro-LEDs. Subsequently, we present the full-color monolithic InGaN micro-LEDs, which stack red (R), green (G), and blue (B) epitaxial layers through tunnel junctions. The entire structure is grown epitaxially by metal organic chemical vapor deposition. Micro-LEDs with a mesa size of 20×20 μm 2 for RGB are fabricated. The red micro-LED exhibits emission with a peak wavelength of 650 nm at an injection current density of 1 A/cm 2 , with a dominant wavelength of approximately 620 nm, achieving a true red emission. Even under an injection of 100 A/cm 2 , it can still maintain a dominant wavelength of over 600 nm. The true red emission and broad color gamut coverage of the full-color monolithic InGaN micro-LEDs demonstrate their significant potential for applications in micro-LED display.

Sidewall Suppression and Top Surface Enhancement of Light Extraction Efficiency in Vertically Stacked Full‐Color Micro‐LEDs Based on L‐Shaped Metal Walls

2025-06-23

H. X. Guo , Jun He , Jie Sun +7 more | Advanced Electronic Materials

Abstract Micro light‐emitting diodes (Micro‐LEDs) are regarded as the core of next‐generation display technology due to their high brightness and energy efficiency. However, the reduction in the size of Micro‐LEDs … Abstract Micro light‐emitting diodes (Micro‐LEDs) are regarded as the core of next‐generation display technology due to their high brightness and energy efficiency. However, the reduction in the size of Micro‐LEDs has led to increased manufacturing challenges and exacerbated issues such as sidewall emission, which hinder the development of high‐pixel‐density displays. This paper proposes a vertically stacked Micro‐LED design based on an L‐shaped metal wall structure, aiming to suppress sidewall emission and enhance top light extraction efficiency (LEE). Through parameter scanning, the dimensions of the Micro‐LED and the thickness of the epitaxial layer are optimized. Combined with inclined sidewalls and the reflective structure of the L‐shaped metal wall, the optical characteristics of red, green, and blue Micro‐LEDs are analyzed using ray‐tracing simulations. The sidewall emission is significantly reduced (with a maximum reduction of 68.04% compared to vertically stacked Micro‐LEDs without metal walls), and top light emission is enhanced (the LEE within ±90° direction for blue, green, and red light increased by 196.18%, 51.69%, and 3.45%, respectively, compared to stacked Micro‐LEDs without metal walls). The simulation results demonstrate the potential of the L‐shaped metal wall in vertically stacked full‐color Micro‐LED displays, providing a new approach to suppressing optical crosstalk and improving display performance.

Comparative study of hot carrier induced degradation in AlGaN/GaN and InAlGaN/GaN HEMTs with AlN spacer

2025-06-23

Tien-Han Yu , Yi‐Fan Tsao , Yu-Lin Chen +2 more | Japanese Journal of Applied Physics

Abstract This article investigates the degradation phenomenon of Y-gate AlGaN/GaN and InAlGaN/GaN HEMTs with AlN spacers under hot carrier injection (HCI) stress. The analysis focused on the degradation of threshold … Abstract This article investigates the degradation phenomenon of Y-gate AlGaN/GaN and InAlGaN/GaN HEMTs with AlN spacers under hot carrier injection (HCI) stress. The analysis focused on the degradation of threshold voltage (ΔVTH), transconductance (Gm), and drain current (ID) of the devices subject to a 10,000-second HCI stress test. AlGaN/GaN HEMTs showed a ΔVTH shift of 0.099 V and an 18.26% ID reduction, while InAlGaN/GaN HEMTs exhibited a slightly larger ΔVTH shift (0.135 V) but a smaller ID degradation (13.62%). The difference results from the lattice mismatch from low In doping concentrations but a higher 2DEG density compensates for trap-induced scattering, resulting in improved carrier transport and greater electrical stability. InAlGaN/GaN devices also had much lower transconductance degradation (11 mS/mm) than AlGaN/GaN devices (56 mS/mm). The findings underscore the benefits of the AlN spacer and In incorporation in improving polarization, interface quality, and reliability, showing promise for long-term, high-performance applications.

High-efficiency p-InGaN/n-InGaN single homojunction solar cell derived by numerical simulation

2025-06-23

Peverga R. Jubu , Mohammed K. Omar , Mohd Zamir Pakhuruddin | Physica Scripta

Abstract The indium gallium nitride (InGaN) material has emerged as a promising candidate for solar cells due to its wide bandgap range of 0.7 to 3.42 eV, which enables enhanced … Abstract The indium gallium nitride (InGaN) material has emerged as a promising candidate for solar cells due to its wide bandgap range of 0.7 to 3.42 eV, which enables enhanced spectral absorption. However, the reported power conversion efficiency (PCE) of InGaN-based single-junction solar cell is relatively low. This simulation work by SCAPS-1D reports a pacesetting PCE of 35.130% for p-In0.5Ga0.5N/n-In0.75Ga0.25N single homojunction solar cell. The PCE exceeds the Shockley-Queisser (SQ) efficiency limit for single-junction solar cells with bandgap near ~1.34 eV. The layer thickness, carrier density and defect density are optimized to produce the high PCE. The PCE is realized with bandgaps of 1.70 and 1.11 eV for the p-type and n-type materials respectively, to enable optimum absorption of wide range of the solar spectrum. The PCE achieved could be ascribed to the maximum absorption capability of the narrow bandgap, optimum thickness (3 µm) and doping concentration (1021 cm-3) of the n-type layer. Temperature effect shows decreasing PCE with rising temperature. Front and back contact work function (WF) studies reveal that Device 1 simulated under flat band and Device 2 under front (7.08 eV) and back (5.32 eV) WF achieve the highest and equivalent PCE value of 35.130%.

Damage Mechanism Analysis of High Field Stress on Cascode GaN HEMT Power Devices

2025-06-22

Shuo Su , Yanrong Cao , Weiwei Zhang +7 more | Micromachines

A series of problems, such as material damage and charge trap, can be caused when GaN HEMT power devices are subjected to high field stress in the off-state. The reliability … A series of problems, such as material damage and charge trap, can be caused when GaN HEMT power devices are subjected to high field stress in the off-state. The reliability of GaN HEMT power devices affects the safe operation of the entire power electronic system and seriously threatens the stability of the equipment. Therefore, it is particularly important to study the damage mechanism of GaN HEMT power devices under high field conditions. This work studies the degradation of Cascode GaN HEMT power devices under off-state high-field stress and analyzes the related damage mechanism. It is found that the high field stress in the off-state will generate a positive charge trap in the oxide layer of the MOS device in the cascade structure. Moreover, defects occur in the barrier layer and buffer layer of GaN HEMT devices, and the threshold voltage of Cascode GaN HEMT power devices is negatively shifted, and the transconductance is reduced. This study provides an important theoretical basis for the reliability of GaN HEMT power devices in complex and harsh environments.

A comparative study of threading dislocations in AlGaN/GaN heterostructures grown on Si substrates with different buffer structures

2025-06-21

Shuang Zhao , C. Cai , Qizhi Li +7 more | Materials Science in Semiconductor Processing

Band Gaps of Hexagonal ScN and YN Multilayer Materials

2025-06-21

M. Winiarski | Materials

The structural parameters and electronic structures of Sc- and Y-based nitride semiconductors that adopted hexagonal BN-like atomic sheets were investigated with calculations based on density functional theory (DFT). A hybrid … The structural parameters and electronic structures of Sc- and Y-based nitride semiconductors that adopted hexagonal BN-like atomic sheets were investigated with calculations based on density functional theory (DFT). A hybrid exchange-correlation functional and spin–orbit coupling were employed for studies on the band structures. A strong variation in the band gap type, as well as the width, was revealed not only between the monolayer and bulk materials but also between the multilayer systems. An exceptionally wide range of band gaps from 1.39 (bulk) up to 3.59 eV (three layers) was obtained for two-dimensional materials based on ScN. This finding is related to two phenomena: significant contributions of subsurface ions into bands that formed a valence band maximum and pronounced shifts in conduction band positions with respect to the Fermi energy between the multilayer systems. The relatively low values of the work function (below 2.36 eV) predicted for the few-layer YN materials might be considered for applications in electron emission. In spite of the fact that the band gaps of two-dimensional materials predicted with hybrid DFT calculations may be overestimated to some extent, the electronic structure of homo- and heterostructures formed by rare earth nitride semiconductors seems to be an interesting subject for further experimental research.

Differences between differential phase contrast and electron holographic measurements of a GaN p-n Junction

2025-06-21

Laura Niermann | Ultramicroscopy

Effect of the Buffer Layers on the Strain Distribution in GaN‐Based Power Transistors using Surface‐Enhanced Raman Spectroscopy

2025-06-21

Jiahao Kang , Jung Ki Park , Jaesun Kim +6 more | physica status solidi (b)

Ex situ room‐temperature strain profiling is analyzed by selectively obtaining surface‐specific Raman spectra as a function of the distance from the surface in GaN‐based power electronic devices. With obliquely truncated … Ex situ room‐temperature strain profiling is analyzed by selectively obtaining surface‐specific Raman spectra as a function of the distance from the surface in GaN‐based power electronic devices. With obliquely truncated structures and by optimizing the surface plasmon resonance of Ag nanoparticles attached to the surface, it becomes possible to observe the development of the strain relaxation process through the epilayer thickness. The initial GaN strain varies depending on the thickness of the AlN buffer. When the thickness of AlN buffer layer is relatively thick, initial strong compressive strain is generated in the GaN epilayers. In contrast, when AlN thickness is thin, then initial strain in GaN is tensile, and the strain reversal is measured after certain thickness. This strain reversal is attributed to the insertion of thin AlGaN interlayers, which can generate compressive strain in the GaN grown on a Si substrate and played a crucial role in altering the overall strain evolution.

Analysis of the External Quantum Efficiency of 233 nm Far‐Ultraviolet‐C‐Light Emitting Diodes with Distributed Polarization Doped p‐AlGaN‐Layers

2025-06-20

Anton Muhin , Tim Kolbe , F. Bilchenko +7 more | physica status solidi (RRL) - Rapid Research Letters

AlGaN‐based far‐ultraviolet‐C light emitting diodes (far‐UVC LEDs) with an emission wavelength of 233 nm and a peak external quantum efficiency () of 1% are explored to derive the radiative recombination … AlGaN‐based far‐ultraviolet‐C light emitting diodes (far‐UVC LEDs) with an emission wavelength of 233 nm and a peak external quantum efficiency () of 1% are explored to derive the radiative recombination efficiency (), the light extraction efficiency (), and the carrier injection efficiency (). In order to investigate the over a wide range of current density, and exclude the effect of heating, continuous wave and pulsed electroluminescence measurements are performed on far‐UVC LEDs with distributed polarization doped p ‐AlGaN layers. By applying the ABC‐model based Titkov–Dai method and calibrated Monte Carlo ray‐tracing simulations, a maximum of , a , and a can be determined. The different efficiency parameters of the 233 nm far‐UVC LEDs are compared to state‐of‐the‐art AlGaN‐based 265 nm LEDs and InGaN multi quantum well blue LEDs. In this context, strategies for most promising approaches to advance the of far‐UVC LEDs are discussed.

Adsorption Characteristics of an AlGaN/GaN Heterojunction on Potassium Ions

2025-06-20

Yan Dong , Mengmeng Li , Yanli Liu +7 more | Molecules

Slight changes in potassium levels can affect health. Therefore, rapid, reliable, and quantitative determination of potassium ion content is important for medical diagnosis. AlGaN, as a semiconductor material with good … Slight changes in potassium levels can affect health. Therefore, rapid, reliable, and quantitative determination of potassium ion content is important for medical diagnosis. AlGaN, as a semiconductor material with good biocompatibility, has many advantages in the development of new potassium ion sensors. Understanding the adsorption behavior of a specific ion on the AlGaN surface and the eventual effect on AlGaN/GaN’s heterostructure interface is the key to obtaining high-performance nitride sensors. In this paper, we calculated the changes in the density of states and energy bands of the material after AlGaN adsorbed potassium ions through first-principles simulation. Combined with two-dimensional device simulation software, the changes in device performance caused by the changes in material properties are presented. The simulation results show that the adsorption of a single potassium ion can cause a current change in the order of milliamperes, providing a theoretical reference for the subsequent development of high-sensitivity potassium ion sensors.

MOCVD-grown, ultra-thin barrier AlN/GaN/AlN HEMTs fabricated using commercial GaN foundry process for Ka-band operation

2025-06-20

Reet Chaudhuri , Kyle M. Bothe , Antonio T. Lucero +5 more | Applied Physics Express

Abstract This work presents AlN/GaN/AlN HEMTs on 4-inch SiC fabricated using a commercial 150 nm RF GaN foundry process. High electrical performance uniformity across the wafer surface is demonstrated. The … Abstract This work presents AlN/GaN/AlN HEMTs on 4-inch SiC fabricated using a commercial 150 nm RF GaN foundry process. High electrical performance uniformity across the wafer surface is demonstrated. The thin 3 nm AlN barrier, low ohmic contact resistances (0.09 Ω.mm), and high-density (1.26 x 10 13 cm -2 ) 2DEG channel results in high transconductances of ~640 mS/mm (maximum of 736 mS/mm) and on-currents ~1.5 A/mm. A peak power output of 2.68 W/mm at PAE of 32% at Ka-band is measured. These results represent a significant step towards technology maturity for the AlN/GaN/AlN HEMTs by demonstrating their compatibility with current GaN foundry processes.

Combination Electro-Optical and Thermo-Optical Phase Tuner in Aluminum Nitride

2025-06-19

Nikolay Videnov , Michal Bajcsy | Optical Materials Express

Impact of low-temperature AlN interlayer on quality and residual stress of AlN films deposited by MOCVD on Si (111) substrate

2025-06-19

Yaxin Wang , Binghui Lin , Yuqi Ren +4 more | Applied Physics A

Influence of p-GaN gate airgap in p-GaN AlGaN/GaN HEMTs for improved DC performance

2025-06-19

Muhaimin Haziq , Hiroshi Kawarada , Shaili Falina +1 more | Research Square (Research Square)

<title>Abstract</title> This study proposes a novel p-GaN AlGaN/GaN high-electron-mobility transistor (HEMT) structure incorporating a gate airgap to address gate leakage and high electric field issues. Comprehensive device simulations conducted using … <title>Abstract</title> This study proposes a novel p-GaN AlGaN/GaN high-electron-mobility transistor (HEMT) structure incorporating a gate airgap to address gate leakage and high electric field issues. Comprehensive device simulations conducted using COMSOL Multiphysics show that the airgap-integrated design enhances the breakdown voltage by 47.7% and reduces gate leakage current by 15% compared to conventional devices. These improvements stem from the redistribution and suppression of peak electric fields near the gate edge, alleviating common leakage mechanisms typically observed in HEMTs. Additionally, the modified structure supports a 35% increase in maximum drain current while maintaining a threshold voltage near 0 V, which is favorable for fail-safe operation in power applications. These findings highlight the promise of gate airgap integration as an effective design strategy for enhancing the performance and long-term reliability of AlGaN/GaN HEMTs in future high-power electronics.

Enhanced drain current density in AlGaN/GaN CAVET through multi-channel composite isolation layers

2025-06-19

Yanjun Wu , Xiaobing Luo , Lin Zhang +2 more | Semiconductor Science and Technology

Abstract In this paper, we propose a high-current-density AlGaN/GaN current aperture vertical electron transistor (CAVET) that utilises multi-channel composite isolation layers. This innovative structure ingeniously incorporates an isolation layer within … Abstract In this paper, we propose a high-current-density AlGaN/GaN current aperture vertical electron transistor (CAVET) that utilises multi-channel composite isolation layers. This innovative structure ingeniously incorporates an isolation layer within the current blocking layer (CBL), thereby effectively mitigating the depletion effect of P+GaN on the channel. Furthermore, a multi-channel design featuring a SiO2 channel isolation layer is employed. This design addresses the issue of mutual depletion of electron gas between multiple channels in vertical structures, thereby significantly enhancing the device's output capability. The results demonstrate that the proposed structure has a threshold voltage (Vth) of 2.81 V and a drain saturation output current (Isat.D) of 3683 mA/mm, representing an 188.6% increase over the basic single-channel trench CAVET. Moreover, the breakdown voltage (BV) of the designed device is 2426 V, with a specific on-resistance (Ron,sp) of 2.90 mΩ·cm². Compared to the basic single-channel trench CAVET, the figure of merit (FOM) is improved by 63.7%.

Degradation behaviors of deep ultraviolet LEDs: The role of polarization induced doping in p-AlGaN layer

2025-06-19

Jianghong Gao , Qiushuang Chen , Hong Yu Liu +7 more | Journal of Physics D Applied Physics

Abstract Polarization-induced doping in p-AlGaN consisting composition gradient AlGaN has been widely utilized in AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance hole injection. Yet the presence of polarization … Abstract Polarization-induced doping in p-AlGaN consisting composition gradient AlGaN has been widely utilized in AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance hole injection. Yet the presence of polarization doping on the degradation behaviors of DUV-LED still remains largely unexplored. In this work, time-dependent electrical, optical properties and degradation mechanisms of 273 nm AlGaN-based DUV-LEDs with and without polarization doping were comprehensively investigated. Compared with DUV-LED incorporating bulk p-AlGaN, polarization-doped DUV-LED reveals lower leakage current, higher output power and longer lifetime due to its unique compositionally graded structure. The external quantum efficiency (EQE) versus current density (J) curves before and after electrical stress were fitted by the ABC + f(n) model. Four-times enhancement in Auger recombination coefficient was obtained for conventional LED after aging, while 185% increased non-radiative recombination coefficient was identified in polarization doped DUV-LEDs, suggesting different roles played between bulk and polarization-doped p-AlGaN during device aging process.

Schottky Contact Degradation and Dislocations in AlGaN‐GaN HEMTs

2025-06-19

Yongkun Sin , Andrew C. Hall , Laurent Matala‐tala +6 more | physica status solidi (a)

GaN power amplifiers based on AlGaN‐GaN high electron mobility transistor (HEMT) technology are finding applications in space satellite systems that require high voltage, high power, and high efficiency operation. In … GaN power amplifiers based on AlGaN‐GaN high electron mobility transistor (HEMT) technology are finding applications in space satellite systems that require high voltage, high power, and high efficiency operation. In recent years, leading GaN HEMT manufacturers have reported excellent performance characteristics, and several research groups have proposed degradation mechanisms, but their long‐term reliability especially under high electric field operation in space environments remains a major concern. For AlGaN‐GaN HEMTs to be successfully deployed in space satellite systems, their reliability and failure mechanisms need to be understood through the physics of failure investigation. Two types of HEMT structures are used to investigate i) a new failure mechanism—Schottky contact degradation in RF AlGaN‐GaN HEMTs with Ni‐Pd‐Au Schottky contact—and ii) effects of threading dislocations on electrical characteristics of DC AlGaN‐GaN HEMTs grown on semi‐insulating (SI) SiC and GaN substrates.

Red luminescence band in undoped GaN

2025-06-18

M. A. Reshchikov | Journal of Luminescence

Impacts of ultra-high-pressure annealing on undoped and ion-implanted GaN studied by photoluminescence measurements

2025-06-18

Kohei Shima , Tetsuo Narita , Akira Uedono +4 more | Journal of Applied Physics

Selective-area doping of GaN using ion implantation (I/I) followed by ultra-high-pressure annealing (UHPA) under 1-GPa-N2 has emerged as a promising technique for GaN power devices. In this article, the impacts … Selective-area doping of GaN using ion implantation (I/I) followed by ultra-high-pressure annealing (UHPA) under 1-GPa-N2 has emerged as a promising technique for GaN power devices. In this article, the impacts of UHPA on the midgap recombination centers (MGRCs) in undoped, Si-implanted, Mg-implanted, and Mg/N-implanted GaN epitaxial layers are described based on the results of photoluminescence (PL) and time-resolved PL measurements. For undoped GaN, PL lifetimes at 300 K for the near-band-edge emission decreased with increasing the annealing temperature (Ta), indicating higher Ta increased the concentration of MGRCs. In contrast, for I/I-GaN, PL lifetimes or PL intensities at 300 K for the near-band-edge emission increased with increasing Ta, indicating higher Ta decreased the concentration of MGRCs originating from the I/I-induced vacancy-type defects comprising Ga and N vacancies [e.g., (VGaVN)3]. Nevertheless, MGRC concentrations in I/I-GaN after UHPA remained several orders of magnitude higher than in undoped GaN. Additional N-I/I onto Mg-implanted GaN followed by UHPA at Ta = 1480 °C enhanced the activation of a Mg acceptor substituted on a Ga site (MgGa) and decreased the concentration of MGRCs. For Mg- and Mg/N-implanted GaN, the progressive activation of MgGa acceptors with increasing Ta was confirmed. However, the PL lifetimes for Mg- and Mg/N-implanted GaN with Mg concentrations higher than 1 × 1018 cm−3 were limited to shorter than 1 ps. To fabricate reliable p-contacts and electron inversion layers using Mg- or Mg/N-I/I combined with UHPA, it is crucial to eliminate or etch away residual defective layers near the surface, which limits the minority carrier lifetime to below 1 ps.

Ab Initio Elucidation of the Nature of the Bonding of Tetrahedral Nitrides (BN, AlN, GaN, and InN), Hexagonal BN, and Graphene

2025-06-18

Paweł Strąk , Konrad Sakowski , Paweł Kempisty +3 more | Materials

Recent measurements of the band properties of AlN and GaN by fluorescence yield absorption and soft X-ray emission spectroscopies revealed that their valence band (VB) is composed of two separate … Recent measurements of the band properties of AlN and GaN by fluorescence yield absorption and soft X-ray emission spectroscopies revealed that their valence band (VB) is composed of two separate subbands. The upper VB subband of GaN is composed of gallium sp and nitrogen p orbitals; the lower subband consists of metal d and nitrogen s orbitals. These findings were confirmed by extensive ab initio simulations. These results are not consistent with the standard tetrahedrally coordinated semiconductors, which are bonded by sp3-hybridized orbitals of metal and nonmetal atoms. The new analysis techniques and ab initio simulations create a new picture, allowing the calculation of overlap integrals to determine the bond order in these crystals. According to these results, bonding occurs between resonant p-states of nitrogen and sp3-hybridized metal orbitals in tetrahedral nitrides, allowing tetrahedral symmetry to be maintained. A similar resonant bonding mechanism is observed in hexagonal BN, where the p orbitals of nitrogen create three resonant states necessary for maintaining the planar symmetry of the lattice. In addition, nonresonant π-type bonds in BN are created by the overlap of pz orbitals of boron and nitrogen. BN bonding differs from that in graphene, where carbon states are fully sp2-hybridized. Additionally, π-type bonds in graphene have no ionic contributions, which leads to the formation of Dirac states with linear dispersion close to the K point, closing the band gap.

Data-driven small-signal modeling of AlGaN/InGaN/GaN high electron mobility transistor using multi-layered ensemble learning

2025-06-17

Neda Ahmad , Sonam Rewari , Vandana Nath | Journal of the Korean Physical Society

Point defect luminescence associated with stacking faults in magnesium doped zincblende GaN

2025-06-17

Xiuyuan Xu , Martin Frentrup , Gunnar Kusch +7 more | Journal of Applied Physics

The luminescence characteristics and the relation between the distribution of impurities and stacking faults (SFs) in Mg-doped zincblende gallium nitride (zb-GaN:Mg) have been investigated by cathodoluminescence (CL) and atom probe … The luminescence characteristics and the relation between the distribution of impurities and stacking faults (SFs) in Mg-doped zincblende gallium nitride (zb-GaN:Mg) have been investigated by cathodoluminescence (CL) and atom probe tomography (APT). Four peaks have been identified in the CL emission spectrum, and the possible related recombination mechanisms have been proposed. The main peak at 3.23 eV is associated with excitonic transitions, while the other three, having lower energies at about 3.15, 3.02, and 2.92 eV, respectively, are related to donor-to-acceptor (DAP) transitions involving different acceptor energy levels. These DAP peaks were significantly more intense on or close to SFs compared to the surrounding defect-free material, indicating an enrichment of point defects near SFs. This finding was supported by APT measurements, where Mg showed a tendency to segregate toward SFs in zb-GaN.

Understanding carrier dynamics in GaN-based blue light-emitting diodes by self-consistent analysis of current, voltage, internal quantum efficiency, and forward capacitance

2025-06-17

Jong‐In Shim , Dong‐Soo Shin | Journal of Applied Physics

A self-consistent analysis of current, voltage, internal-quantum efficiency, and forward capacitance of the GaN-based blue light-emitting diode (LED) is presented to obtain the detailed information on the carrier dynamics inside … A self-consistent analysis of current, voltage, internal-quantum efficiency, and forward capacitance of the GaN-based blue light-emitting diode (LED) is presented to obtain the detailed information on the carrier dynamics inside and outside the active quantum well (QW). In the analysis, the forward capacitance of the device plays a crucial role in providing additional information on the region where the nonradiative recombination occurs. The experimental data from a GaN-based blue LED are used in the analysis to show how charge carriers distribute inside and outside the QW and how carrier lifetimes and radiative/nonradiative currents behave as functions of applied voltage and current. It is shown that charge carriers recombine in the well with an-order-of-magnitude-higher density than in the barrier/interlayer.

A Novel High-Gain Circularly Polarized Filtenna Based on Coaxial Structure

2025-06-16

D. Zhang , Ke Zhu , Sihua Qi | Radioengineering

Nanoscopic structural and emission properties of red InGaN hybrid single quantum wells

2025-06-16

Zhaozong Zhang , Ryota Ishii , Kanako Shojiki +4 more | Applied Physics Letters

Using atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM)-photoluminescence (PL) spectroscopy (SNOM-PL), we study the nanoscopic structural and emission properties of a red InGaN hybrid single quantum well … Using atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM)-photoluminescence (PL) spectroscopy (SNOM-PL), we study the nanoscopic structural and emission properties of a red InGaN hybrid single quantum well (SQW), consisting of a blue and a red InGaN SQW. AFM images reveal the presence of threading-dislocation (TD)-related V-pits and shallow trench defects. The trench defects are classified into three categories on the basis of their height relative to a flat QW: lowered-, level-, and raised-center trench defects. SNOM-PL images demonstrate that TDs and all types of shallow trench defects exhibit a low emission intensity, indicating that they act as non-radiative recombination centers. Unlike previous studies on low-In content samples, all the trench defects exhibit a low emission intensity in our high-In content sample because of In segregation. Given the correlation of dark emission positions between the blue and red emissions, as well as the lower screw-type TD density at the surface than at the n-GaN layer, screw-type TDs should be one of the triggers in the formation of shallow trench defects. Therefore, to enhance the external quantum efficiency of hybrid InGaN red LEDs, it is crucial to suppress In segregation within shallow trench defects and decrease screw-type TD density.

Epitaxial strain reconfiguration of AlGaN multiple heterojunctions for high-responsivity high-speed UV detection

2025-06-16

Zesheng Lv , Zhuoya Peng , Yv Yin +4 more | Applied Physics Letters

Achieving simple and efficient strain engineering remains a persistent challenge in AlGaN-based material and device research, thereby substantially hampering the realization of the inherent material advantages. In this study, a … Achieving simple and efficient strain engineering remains a persistent challenge in AlGaN-based material and device research, thereby substantially hampering the realization of the inherent material advantages. In this study, a strain reconfiguration strategy utilizing a medium-temperature AlN (MT-AlN) interlayer is proposed. By optimizing the MT-AlN thickness at 1000 °C, tensile strain originating from the GaN template is systematically released through interfacial relaxation and lattice redistribution within the interlayer. Additionally, the engineered configuration also establishes a coherent crystalline template with programmable strain states for subsequent epitaxial growth. With a 25-nm optimized interlayer, crack-free Al0.35 ∼ 0GaN multiple heterojunctions are epitaxially grown on the GaN template with slight compressive strain and nearly no additional dislocations. The resultant high-crystallinity AlGaN heterostructures enable the UV photodetector to achieve high responsivity (maximum 1.4 × 103 A/W), ultrafast response speed (0.6/25.4 ns rise/fall time), and remarkable operational stability simultaneously. All these collectively validate the MT-AlN strain reconfiguration as a viable pathway for the advancement of AlGaN-based optoelectronic devices.

Efficiency cliff in scaling InGaN light-emitting diodes down to submicron

2025-06-16

J. Lee , Yi-Chen Chiu , C. Bayram | Applied Physics Letters

The top-down submicron fabrication of blue-emitting light-emitting diodes on Qromis Substrate Technology substrates is reported. Light-emitting diodes with mesa sizes as small as 250 × 250 nm2 show ideal forward … The top-down submicron fabrication of blue-emitting light-emitting diodes on Qromis Substrate Technology substrates is reported. Light-emitting diodes with mesa sizes as small as 250 × 250 nm2 show ideal forward voltage and low leakage current density. It is observed that sidewall treatment and passivation methods used in micro-light-emitting diodes (2–20 μm) do not lead to the same level of sidewall recombination suppression for submicron ones (&lt;1 μm), as evidenced by a ∼70% decrease in peak external quantum efficiencies when mesa sizes are scaled from 2 μm down to 250 nm. This is attributed to the lateral carrier diffusion being comparable to the mesa size, regardless of the sidewall passivation and recovery. The results call for rethinking the impact of sidewalls in emerging top-down fabricated (sub)micrometer-light-emitting diodes.

Sub-terahertz AlN/GaN resonant tunneling diode oscillators using split-ring resonators integrated with bow-tie antennas

2025-06-16

Masahiro Murayama , Hisayoshi Motobayashi , Yukio Hoshina +5 more | Applied Physics Letters

We developed sub-terahertz oscillators employing GaN-based resonant tunneling diodes (RTDs) grown on semi-insulating c-plane GaN substrates using metal-organic chemical vapor deposition. The RTDs incorporated a GaN quantum well and AlN … We developed sub-terahertz oscillators employing GaN-based resonant tunneling diodes (RTDs) grown on semi-insulating c-plane GaN substrates using metal-organic chemical vapor deposition. The RTDs incorporated a GaN quantum well and AlN double barriers, with an InGaN layer as part of the collector-side spacer. This InGaN spacer significantly enhanced the resonant tunneling current compared to conventional GaN-only spacers, achieving a peak current density of up to 622 kA/cm2, peak-to-valley current ratio of 1.56, and a maximum negative differential conductance of 7.1 mS/μm2. The oscillator structure featured split-ring resonators integrated with bow-tie antennas, which improved the radiation efficiency on the low-frequency side, facilitating effective electromagnetic wave emission at an intended oscillation frequency. The fabricated AlN/GaN-RTD oscillators exhibited sub-terahertz oscillations in the 88–104 GHz frequency range. These findings contribute to advancing high-frequency sources for sub-terahertz and terahertz applications.

Insight on Self-Emissive μLED Display from Correlations between Surface Current and Efficiency/Emission Properties of Size-Dependent μLEDs

2025-06-16

Woo Jin Baek , Juhyuk Park , Hyun Soo Kim +4 more | ACS Photonics

Novel insights into GaN-HEMT behavior under multi-particle irradiation

2025-06-15

Rijin N.T. , Dinesh Kumar , M. M. Musthafa +1 more | Applied Radiation and Isotopes

Developing a hybrid single band carrier transport model for (Al,Ga)N heterostructures

2025-06-13

Michael O’Donovan , Robert Finn , Patricio Farrell +4 more | Journal of Computational Electronics

Testing microscale light-emitting diodes with a lighter touch

2025-06-13

Xinqin Liao , Ziquan Guo , Zhong Chen | Nature Electronics

High threshold voltage enhancement-mode AlGaN/GaN HEMT with double barrier hybrid gate

2025-06-13

Rukai Jiang , X. Hu , Zhuokun He +4 more | Journal of Vacuum Science & Technology B Nanotechnology and Microelectronics Materials Processing Measurement and Phenomena

This work presents a novel enhancement-mode hybrid p-type gate AlGaN/GaN high electron mobility transistor (HEMT) with a double barrier structure. The double barrier hybrid-gate (DBHG) HEMT yields better performance than … This work presents a novel enhancement-mode hybrid p-type gate AlGaN/GaN high electron mobility transistor (HEMT) with a double barrier structure. The double barrier hybrid-gate (DBHG) HEMT yields better performance than the traditional p-GaN gate HEMTs in terms of threshold voltage and breakdown voltage, which can be attributed to the regulation of the interface electric field in the AlGaN barrier layers. Moreover, the simulated results indicate that the DBHG HEMT exhibits a high threshold voltage of 1.8 V and a breakdown voltage of 995 V. In addition, we discussed the influence of the thickness of each layer in the double barrier layer structure on device performance. This work provides valuable insights for future innovations in the structure design of HEMTs.

Fabrication and investigation of 1200V-class high voltage GaN HEMTs with different design strategies and inter-metal dielectric layers

2025-06-13

Moufu Kong , Yingzhi Luo , Yaowen Zhang +5 more | Semiconductor Science and Technology

Abstract Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) have demonstrated significant potential in the field of power electronics. However, in the 1200V-class high voltage and high current scenarios, the utilization of … Abstract Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) have demonstrated significant potential in the field of power electronics. However, in the 1200V-class high voltage and high current scenarios, the utilization of GaN HEMT devices is considerably less prevalent compared to that of silicon carbide (SiC) devices. In this work, 1200V-class high-voltage and high-current GaN HEMT devices were developed. The effects of various layout structures and parameters on the performance of GaN HEMT power devices were also analyzed and compared. The source/drain centered cell layouts, the positions of the bonding pads, variations in gate-to-drain distance (LGD) and different inter-metal dielectric (IMD) layer configurations are all considered in this study. Through experimental analysis, we compare key electrical performance metrics such as breakdown voltage (BV), threshold voltage (Vth), on-state resistance (RDS,on) and gate/drain leakage current. The results indicate that the BVs of all the fabricated GaN HEMTs are higher than 1400 V, and the BV of our proposed GaN HEMT with floating field plate (FFP-HEMT) are more than 2000 V. The RDS,on of the device is 156.2 mΩ with a specific on-resistance of 10 mΩ cm², which has great application prospects in high-voltage and high-current power electronic systems.

Polarization-induced doping in AlInN/GaN nanowire ultraviolet light-emitting diodes

2025-06-12

Samadrita Das , Mano Bala Sankar Muthu , Phuong Thi Thanh Nguyen +3 more | Journal of Nanophotonics

GaN localization in AlGaN grown by ultra-high-temperature metalorganic vapor phase epitaxy

2025-06-12

Y. Matsubara , Atsushi Tomita , Koji Fujii +4 more | Japanese Journal of Applied Physics

Abstract GaN localization in AlGaN was achieved through ultra-high-temperature metalorganic vapor phase epitaxy. This localization was observed as a hillock structure measuring several micrometers. Localization occurred in the nonlinear region … Abstract GaN localization in AlGaN was achieved through ultra-high-temperature metalorganic vapor phase epitaxy. This localization was observed as a hillock structure measuring several micrometers. Localization occurred in the nonlinear region between the input Al/(Al+Ga) ratio and solid composition (AlN in AlGaN) at 1500 °C under the condition of a high flow rate and a low Al/(Al+Ga) ratio during the simultaneous supply of Al and Ga. X-ray diffraction analysis detected a GaN peak during AlGaN growth, whereas scanning electron microscopy energy dispersive X-ray spectroscopy revealed compositional inhomogeneity of Al and Ga. These findings, which facilitate material localization, can be expected as a future technology for achieving high internal quantum efficiency.

High field performance of Si-doped n-AlN layers grown using pulsed MOCVD

2025-06-12

Abdullah Al Mamun Mazumder , Tariq Jamil , M. Azizar Rahman +3 more | Applied Physics Express

Abstract We report on the study of high-field performance of Si-doped n-AlN layers grown using a pulsed metalorganic chemical vapor deposition (PMOCVD) process. In the past we showed this pulsed … Abstract We report on the study of high-field performance of Si-doped n-AlN layers grown using a pulsed metalorganic chemical vapor deposition (PMOCVD) process. In the past we showed this pulsed doping approach to lead to doping efficiency superior to that in the conventional MOCVD process. Here using them as the drift layer for a quasi-vertical conduction Schottky barrier, we show their ability to withstand high reverse bias voltages and sustain an electrical field as high as 9.9 MV/cm. Our study thus demonstrates the viability of the PMOCVD growth and doping approach to yield n-AlN layers suitable for high current-high voltage devices.

High Response Speed Broadband Photodetectors Based on Poly‐Si/4H‐SiC Heterojunction

2025-06-12

Zihao Li , Mingkun Zhang , Sitian Chen +7 more | physica status solidi (a)

Broadband ultraviolet‐visible‐near‐infrared (UV‐VIS‐NIR) photodetectors (PDs) have been fabricated and demonstrated by combining polycrystalline silicon (poly‐Si) with vanadium‐doped semi‐insulating (SI) 4H‐SiC. Vanadium‐doped deep‐level defects were utilized to enhance the responsivity to … Broadband ultraviolet‐visible‐near‐infrared (UV‐VIS‐NIR) photodetectors (PDs) have been fabricated and demonstrated by combining polycrystalline silicon (poly‐Si) with vanadium‐doped semi‐insulating (SI) 4H‐SiC. Vanadium‐doped deep‐level defects were utilized to enhance the responsivity to VIS and NIR light. A PNP lateral structure is designed in order to expand the depletion region, which enhances the photocurrent of the PDs. These PDs have extremely low dark current of 18 fA at 40 V and high photosensitivity in all detection bands including 1.14 × 10 4 at 310 nm, 1.24 × 10 2 at 500 nm, 1.29 × 10 2 at 990 nm, and 1.54 × 10 2 at 1100 nm. Furthermore, these PDs have a high response speed of rise/fall time of 5.6 ns/169 ns at 40 V bias. In addition, the carrier behavior of the heterojunction under broadband light exposure is analyzed in detail by constructing the energy band diagram. The high sensitivity and response speed make these heterojunction PDs suitable for applications in intelligent driving systems.

Surface Properties of p‐GaN and Formation of Nickel Metal Contacts

2025-06-12

Mikko Miettinen , Vesa Nuutila , Zahra Jahanshah Rad +7 more | Advanced Materials Interfaces

Abstract Nickel (Ni) is the key component in ohmic contacts for Mg‐doped p‐GaN, but the detailed formation mechanisms of the ohmic contact have not yet been understood. In this work, … Abstract Nickel (Ni) is the key component in ohmic contacts for Mg‐doped p‐GaN, but the detailed formation mechanisms of the ohmic contact have not yet been understood. In this work, the effect of potassium hydroxide (KOH)‐based chemical treatment on the surface of p‐GaN is investigated using X‐ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and low‐energy electron diffraction (LEED). Ni metal contacts on the chemically treated p‐GaN surface are studied using transfer length method (TLM) and synchrotron radiation photoelectron spectroscopy (SR‐XPS). The chemical treatment of p‐GaN improves the brightness of the (1x1) hexagonal diffraction pattern in LEED and keeps the 2D terrace structure in STM visible. Concomitantly, XPS shows that the amount of O, C, and Mg–O bonds at the surface were reduced. Ni/p‐GaN provided an ohmic contact after annealing in ultra‐high vacuum (UHV) at 500 °C. Simultaneously, SR‐XPS shows the diffusion of Ga to Ni and the formation of a previously unreported Ga 3d component, which has a surprisingly narrow line shape, indicating that it originates from a crystalline interface phase. Diffusion of Ga is discussed to cause Ga vacancies and acceptor levels in the bandgap increasing carrier tunneling, thus enabling ohmic contact.

Self-organized morphological and compositional evolution in Al1-xInxN structures on GaN layers

2025-06-12

Dongkyun Kwon , Hyun Jin Choi , Chan Hee Hwang +6 more | Applied Surface Science Advances