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Crystals
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Recent Advances in III-Nitride Semiconductors
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Recent Advances in III-Nitride Semiconductors

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Materials for Energy Applications".

Deadline for manuscript submissions: closed (15 February 2023) | Viewed by 43512

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Peng Chen

E-Mail Website
Guest Editor
1. Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China
2. Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, China
Interests: semiconductor optoelectronics; plasmon photonics; semiconductor micro/nano structure; solid-state electronics and power electronic devices; III-nitrides on Si substrates
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Zhizhong Chen

E-Mail Website
Guest Editor
State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
Interests: III-nitride device physics; LED; GaN-based micro-nano light-emitting structure; GaN-based micro-nano device; LED light source for regulating the biological rhythm
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

GaN and the group-III nitride family are typical wide bandgap semiconductors. The interest in group-III nitrides lies in their irreplaceable and efficient blue-UV luminescence capability. Recent progress in GaN-based material quality and device design relies on well-mastered techniques of material growth and the formation of desired structures with other elements. This offers a high possibility of creating high-quality materials and diverse functional devices. Among the ways that we can improve the internal quantum efficiency of radiative recombination, coupling with localized surface plasmons (LSPs) is a very promising method. When quantum wells (QWs) are placed in the evanescent field of LSPs, they can be strongly coupled with the LSPs under certain conditions. There may also be other energy induction mechanisms that improve the radiative recombination of the excitons locally from the LSP resonance—a topic which is still open. The resonance effects caused by photon–electron interaction are always the focus of attention in semiconductor optoelectronics. Determining how to effectively modulate photon behavior is another important issue in this area.

GaN is also a promising candidate for next-generation power electronic applications because of its outstanding material properties, but its potential is far from being realized. Regarding whether GaN can be competent in the field of ultra-high voltage (UHV, >10kV) applications, there is currently a huge controversy in the community, especially under the strong background of SiC in this field, although GaN has a farther limit than SiC based on the nature of the materials.

Therefore, we invite researchers to contribute to this Special Issue on “Recent Advances in III-Nitride Semiconductors”, covering a broad spectrum of topics from the study of materials, micro/nano structures, and novel functional devices to new applications in frontier fields.

The topics include but are not limited to:

  • Growth of GaN-based materials and micro/nanostructures;
  • Characterization of the materials and the heterostructures;
  • GaN-based novel devices, including emission, detection, and power devices;
  • Application and integration of the materials and novel devices in novel electronics and photonics

Prof. Dr. Peng Chen
Prof. Dr. Zhizhong Chen
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Nitrides
  • GaN
  • AlGaN
  • InGaN
  • Heterostructures
  • Epitaxy
  • Electro-optics devices
  • Micro-electronics devices
  • Power devices
  • Tunable devices
  • Photonic crystal enhanced light-matter interaction
  • Photonic crystal and plasmonics

Related Special Issue

Published Papers (16 papers)

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Research

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7 pages, 1225 KiB  
Article
Proposal for Deep-UV Emission from a Near-Infrared AlN/GaN-Based Quantum Cascade Device Using Multiple Photon Up-Conversion
by Daniel Hofstetter, David P. Bour and Hans Beck
Crystals 2023, 13(3), 494; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13030494 - 13 Mar 2023
Cited by 2 | Viewed by 1381
Abstract
We propose the use of an n-doped periodic AlN/GaN quantum cascade structure for the optical up-conversion of multiple near-infrared (near-IR) photons into deep-ultraviolet (deep-UV) radiation. Without applying an external bias voltage, the active region of such a device will (similar to an un-biased [...] Read more.
We propose the use of an n-doped periodic AlN/GaN quantum cascade structure for the optical up-conversion of multiple near-infrared (near-IR) photons into deep-ultraviolet (deep-UV) radiation. Without applying an external bias voltage, the active region of such a device will (similar to an un-biased quantum cascade laser) resemble a sawtooth-shaped inter-subband structure. A carefully adjusted bias voltage then converts this sawtooth pattern into a ‘quantum-stair’. Illumination with λ = 1.55 µm radiation results in photon absorption thereby lifting electrons from the ground state of each main well into the first excited state. Three additional GaN quantum wells per period then provide by LO-phonon-assisted tunneling a diagonal transfer of these electrons towards the ground level of the neighboring period. From there, the next near-infrared (near-IR) photon absorption, electron excitation, and partial relaxation takes place. After 12 such absorption, transfer, and relaxation processes, the excited electrons have gained a sufficiently high amount of energy to undergo in the final AlN-based p-type contact layer an electron-hole band-to-band recombination. By employing this procedure, multiple near-IR photons will be up-converted to produce deep-UV radiation. Since for a wavelength of 1.55 µm very powerful near-IR pump lasers are readily available, such an up-conversion device will (even at a moderate overall conversion efficiency) potentially result in an equal or even higher output power than the one of an AlN-based p-n-junction light-emitting diode. The proposed structures are therefore very interesting for applications such as ultra-high-resolution photolithography or printing, water purification, medical equipment disinfection, white light generation, or the automotive industry. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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12 pages, 2346 KiB  
Article
MOCVD of InGaN on ScAlMgO4 on Al2O3 Substrates with Improved Surface Morphology and Crystallinity
by Guangying Wang, Yuting Li, Jeremy Kirch, Yizhou Han, Jiahao Chen, Samuel Marks, Swarnav Mukhopadhyay, Rui Liu, Cheng Liu, Paul G. Evans and Shubhra S. Pasayat
Crystals 2023, 13(3), 446; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13030446 - 04 Mar 2023
Cited by 1 | Viewed by 1717
Abstract
ScAlMgO4 (SAM) is a promising substrate material for group III-nitride semiconductors. SAM has a lower lattice mismatch with III-nitride materials compared to conventionally used sapphire (Al2O3) and silicon substrates. Bulk SAM substrate has the issues of high cost [...] Read more.
ScAlMgO4 (SAM) is a promising substrate material for group III-nitride semiconductors. SAM has a lower lattice mismatch with III-nitride materials compared to conventionally used sapphire (Al2O3) and silicon substrates. Bulk SAM substrate has the issues of high cost and lack of large area substrates. Utilizing solid-phase epitaxy to transform an amorphous SAM on a sapphire substrate into a crystalline form is a cost-efficient and scalable approach. Amorphous SAM layers were deposited on 0001-oriented Al2O3 by sputtering and crystallized by annealing at a temperature greater than 850 °C. Annealing under suboptimal annealing conditions results in a larger volume fraction of a competing spinel phase (MgAl2O4) exhibiting themselves as crystal facets on the subsequently grown InGaN layers during MOCVD growth. InGaN on SAM layers demonstrated both a higher intensity and emission redshift compared to the co-loaded InGaN on GaN on sapphire samples, providing a promising prospect for achieving efficient longer-wavelength emitters. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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13 pages, 4419 KiB  
Article
Plasma-Assisted Halide Vapor Phase Epitaxy for Low Temperature Growth of III-Nitrides
by Galia Pozina, Chih-Wei Hsu, Natalia Abrikossova and Carl Hemmingsson
Crystals 2023, 13(3), 373; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13030373 - 22 Feb 2023
Cited by 2 | Viewed by 1156
Abstract
Developing growth techniques for the manufacture of wide band gap III-nitrides semiconductors is important for the further improvement of optoelectronic applications. A plasma-assisted halide phase vapor epitaxy (PA-HVPE) approach is demonstrated for the manufacture of undoped and In-doped GaN layers at ~600 °C. [...] Read more.
Developing growth techniques for the manufacture of wide band gap III-nitrides semiconductors is important for the further improvement of optoelectronic applications. A plasma-assisted halide phase vapor epitaxy (PA-HVPE) approach is demonstrated for the manufacture of undoped and In-doped GaN layers at ~600 °C. A dielectric barrier discharge (DBD) plasma source is utilized for the low-temperature activation of ammonia. The use of the plasma source at a growth temperature of ~600 °C increases the growth rate from ~1.2 to ~4–5 µm/h. Furthermore, the possibility for the growth of InGaN at ~600 °C has been studied. Precursors of GaCl and InCl/InCl3 are formed in situ in the reactor by flowing HCl gas over a melt of metallic Ga and In, respectively. The In concentration was low, in the order of a few percent, as the incorporation of In is reduced by plasma due to the activation of chlorine-containing species that etch the relatively poorly bonded In atoms. Nevertheless, the approach of using plasma for ammonia activation is a very promising approach to growing epitaxial III-nitrides at low temperatures. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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12 pages, 3148 KiB  
Article
Micro-Nanoarchitectonics of Ga2O3/GaN Core-Shell Rod Arrays for High-Performance Broadband Ultraviolet Photodetection
by Ruifan Tang, Guanqi Li, Xun Hu, Na Gao, Jinchai Li, Kai Huang, Junyong Kang and Rong Zhang
Crystals 2023, 13(2), 366; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13020366 - 20 Feb 2023
Cited by 3 | Viewed by 1955
Abstract
This study presents broadband ultraviolet photodetectors (BUV PDs) based on Ga2O3/GaN core-shell micro-nanorod arrays with excellent performance. Micro-Nanoarchitectonics of Ga2O3/GaN core-shell rod arrays were fabricated with high-temperature oxidization of GaN micro-nanorod arrays. The PD based [...] Read more.
This study presents broadband ultraviolet photodetectors (BUV PDs) based on Ga2O3/GaN core-shell micro-nanorod arrays with excellent performance. Micro-Nanoarchitectonics of Ga2O3/GaN core-shell rod arrays were fabricated with high-temperature oxidization of GaN micro-nanorod arrays. The PD based on the microrod arrays exhibited an ultrahigh responsivity of 2300 A/W for 280 nm at 7 V, the peak responsivity was approximately 400 times larger than those of the PD based on the planar Ga2O3/GaN film. The responsivity was over 1500 A/W for the 270–360 nm band at 7 V. The external quantum efficiency was up to 1.02 × 106% for 280 nm. Moreover, the responsivity was further increased to 2.65 × 104 A/W for 365 nm and over 1.5 × 104 A/W for 270–360 nm using the nanorod arrays. The physical mechanism may have been attributed to the large surface area of the micro-nanorods coupled with the Ga2O3/GaN heterostructure, which excited more photogenerated holes to be blocked at the Ga2O3 surface and Ga2O3/GaN interface, resulting in a larger internal gain. The overall high performance coupled with large-scale production makes it a promising candidate for practical BUV PD. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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12 pages, 3175 KiB  
Article
MOCVD-grown β-Ga2O3 as a Gate Dielectric on AlGaN/GaN-Based Heterojunction Field Effect Transistor
by Samiul Hasan, Mohi Uddin Jewel, Scott R. Crittenden, Dongkyu Lee, Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç and Iftikhar Ahmad
Crystals 2023, 13(2), 231; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13020231 - 28 Jan 2023
Cited by 4 | Viewed by 2126
Abstract
We report the electrical properties of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) structures with a Ga2O3 passivation layer grown by metal–organic chemical vapor deposition (MOCVD). In this study, three different thicknesses of β-Ga2O3 [...] Read more.
We report the electrical properties of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) structures with a Ga2O3 passivation layer grown by metal–organic chemical vapor deposition (MOCVD). In this study, three different thicknesses of β-Ga2O3 dielectric layers were grown on Al0.3Ga0.7N/GaN structures leading to metal-oxide-semiconductor-HFET or MOSHFET structures. X-ray diffraction (XRD) showed the (2¯01) orientation peaks of β-Ga2O3 in the device structure. The van der Pauw and Hall measurements yield the electron density of ~ 4 × 1018 cm−3 and mobility of ~770 cm2V−1s−1 in the 2-dimensional electron gas (2DEG) channel at room temperature. Capacitance–voltage (C-V) measurement for the on-state 2DEG density for the MOSHFET structure was found to be of the order of ~1.5 × 1013 cm−2. The thickness of the Ga2O3 layer was inversely related to the threshold voltage and the on-state capacitance. The interface charge density between the oxide and Al0.3Ga0.7N barrier layer was found to be of the order of ~1012 cm2eV−1. A significant reduction in leakage current from ~10−4 A/cm2 for HFET to ~10−6 A/cm2 for MOSHFET was observed well beyond pinch-off in the off-stage at -20 V applied gate voltage. The annealing at 900° C of the MOSHFET structures revealed that the Ga2O3 layer was thermally stable at high temperatures resulting in insignificant threshold voltage shifts for annealed samples with respect to as-deposited (unannealed) structures. Our results show that the MOCVD-gown Ga2O3 dielectric layers can be a strong candidate for stable high-power devices. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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11 pages, 2302 KiB  
Article
Effect of Amorphous Photonic Structure Surface Mounted on Luminous Performances of White LED
by Fei Huang, Yiyong Chen, Jingxin Nie, Chunsheng Shen, Jiulong Yuan, Yukun Guo, Boyan Dong, Lu Liu, Weihua Chen, Zhizhong Chen and Bo Shen
Crystals 2023, 13(1), 6; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13010006 - 20 Dec 2022
Viewed by 1145
Abstract
We fabricated amorphous photonic structures (APSs) with different periods and hole diameters. The GaN-based white light emitting diodes (LEDs) at nominal correlated color temperatures (CCTs) of 5000 and 6000 K were surface mounted by these APSs. The electroluminescence (EL) measurements showed less luminous [...] Read more.
We fabricated amorphous photonic structures (APSs) with different periods and hole diameters. The GaN-based white light emitting diodes (LEDs) at nominal correlated color temperatures (CCTs) of 5000 and 6000 K were surface mounted by these APSs. The electroluminescence (EL) measurements showed less luminous efficiency (LE) and higher CCT than the ones of the virginal white LEDs. However, the LEs of many APS-mounted white LEDs increased compared to white the LEDs without APSs at the same CCTs. A finite-difference time-domain (FDTD) simulation was carried out on the ASPs surface-mounted white LEDs and bidirectional scattering distribution functions (BSDFs) of different emissions were transferred to a Monte Carlo ray tracing simulation. The simulated LEs and CCTs conformed well to the experimental ones. The effects of the blue emission transmission and phosphor concentration were simulated to predict the absolute LE enhancement methods for white LEDs. At last, the hopeful APSs for high Les’ general lighting were discussed. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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8 pages, 1873 KiB  
Article
Investigation of the Effect of ITO Size and Mesa Shape on the Optoelectronic Properties of GaN-Based Micro LEDs
by Aoqi Fang, Hao Xu, Weiling Guo, Jixin Liu, Jiaxin Chen and Mengmei Li
Crystals 2022, 12(11), 1593; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12111593 - 09 Nov 2022
Cited by 1 | Viewed by 1724
Abstract
In this paper, in order to explore the influence of indium tin oxide (ITO) size and mesa shape on the performance of GaN-based micro light emitting diodes (Micro LEDs) on sapphire substrates, Micro LEDs of different sizes with ITO area smaller than or [...] Read more.
In this paper, in order to explore the influence of indium tin oxide (ITO) size and mesa shape on the performance of GaN-based micro light emitting diodes (Micro LEDs) on sapphire substrates, Micro LEDs of different sizes with ITO area smaller than or equal to the light-emitting area were designed and fabricated. The experiment results show that when the ITO area of the Micro LED is equal to the area of the light-emitting area, its optoelectronic performance is significantly better than that of the Micro LEDs whose ITO area is smaller than the area of the light-emitting area. When the light-emitting area size is 40 μm, the wall-plug efficiency (WPE) of the two structures of Micro LEDs can differ by more than 50%. Based on above experiment results, this paper designed and fabricated Micro LEDs with different sizes of square and circular mesa with the same ITO area as the light-emitting area. The experimental results show that the WPE of the circular mesa Micro LED is slightly higher than that of the square mesa Micro LED at low current density. However, as the current density and chip size increase, the performance of the Micro LED with a square mesa is better. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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6 pages, 2680 KiB  
Article
Nickel-Assisted Transfer-Free Technology of Graphene Chemical Vapor Deposition on GaN for Improving the Electrical Performance of Light-Emitting Diodes
by Penghao Tang, Fangzhu Xiong, Zaifa Du, Kai Li, Yu Mei, Weiling Guo and Jie Sun
Crystals 2022, 12(10), 1497; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101497 - 21 Oct 2022
Cited by 2 | Viewed by 1535
Abstract
With the rapid development of graphene technology, today graphene performs well in the application of light-emitting diode (LED) transparent electrodes. Naturally, high-quality contact between the graphene and the GaN underneath is very important. This paper reports a process for nickel-assisted transfer-free technology of [...] Read more.
With the rapid development of graphene technology, today graphene performs well in the application of light-emitting diode (LED) transparent electrodes. Naturally, high-quality contact between the graphene and the GaN underneath is very important. This paper reports a process for nickel-assisted transfer-free technology of graphene chemical vapor deposition on GaN. The nickel film plays the dual role of etching mask and growth catalyst, and is removed by the subsequent “penetration etching” process, achieving good direct contact between the graphene and GaN. The results show that the graphene effectively improves the current spreading of GaN-based LEDs and enhances their electrical performance. This scheme avoids the wrinkles and cracks of graphene from the transfer process, and is not only suitable for the combination of graphene and GaN-based LEDs, but also provides a solution for the integration of graphene and other materials. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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9 pages, 3230 KiB  
Article
Effect of Source Field Plate Cracks on the Electrical Performance of AlGaN/GaN HEMT Devices
by Ye-Nan Bie, Cheng-Lin Du, Xiao-Long Cai, Ran Ye, Hai-Jun Liu, Yu Zhang, Xiang-Yang Duan and Jie-Jie Zhu
Crystals 2022, 12(9), 1195; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12091195 - 25 Aug 2022
Cited by 4 | Viewed by 1667
Abstract
In the current study, the effects of cracks in source field plates (SFPs) on the electrical performance of AlGaN/GaN high electron mobility transistors (HEMTs) are investigated systematically using numerical simulation. In detail, the influence of crack width and junction angle in SFPs on [...] Read more.
In the current study, the effects of cracks in source field plates (SFPs) on the electrical performance of AlGaN/GaN high electron mobility transistors (HEMTs) are investigated systematically using numerical simulation. In detail, the influence of crack width and junction angle in SFPs on device performance is studied. The results indicate that the SFP structure increases the breakdown voltage of a device, but the occurrence of cracks causes premature breakdown, which is confirmed experimentally by the structural analysis of these devices after breakdown. With an increase in crack width, the electrical performance becomes worse. A beveled SFP architecture is proposed by increasing the angle at the SFP junction to reduce the probability of cracking and enhance the reliability of the device. However, with an increase in bevel angle, the modulation effect of the SFP on the channel electric field is gradually weakened. Therefore, it is necessary to balance the relationship between electrical performance and bevel angle according to the actual demands. This work provides potential support for SFP structural optimization design for AlGaN/GaN HEMTs. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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9 pages, 3225 KiB  
Article
Numerical Study of Growth Rate and Purge Time in the AlN Pulsed MOCVD Process
by Wei-Jie Lin and Jyh-Chen Chen
Crystals 2022, 12(8), 1101; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12081101 - 05 Aug 2022
Cited by 2 | Viewed by 1273
Abstract
The relationship between the purge time and the overall growth rate in pulsed injection metal–organic chemical vapor deposition with different V/III ratios is studied by numerical analysis. The transport behavior of TMAl and TMAlNH3 during the process is studied to understand the [...] Read more.
The relationship between the purge time and the overall growth rate in pulsed injection metal–organic chemical vapor deposition with different V/III ratios is studied by numerical analysis. The transport behavior of TMAl and TMAlNH3 during the process is studied to understand the effect of the adductive reaction. The results show that, as the V/III ratio increases, there is a significant reduction in the average growth rate per cycle, without the addition of a purging H2 pulse between the III and V pulses, due to stronger adductive reaction. The adductive reaction can be reduced by inserting a purging pulse of pure H2 between the III and V pulses, but there is a decrease in the overall growth rate due to the longer cycle time. At smaller V/III ratios, the growth rate decreases with increasing purge times, since the gain in reducing the adductive reaction is offset by the detrimental effect of extending the cycle time. The degree of reduction in the adductive reaction is higher for larger V/III ratios. When the benefit of reducing the adductive reaction overcomes the deficiency of the extending cycle time, a remarkable enhancement of the growth rate can be obtained at high V/III ratios by inserting a pure H2 purge pulse between the III and V pulses. A higher overall growth rate can be achieved at higher V/III ratios by choosing an appropriate purge time. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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9 pages, 2627 KiB  
Article
Efficiency Droop and Degradation in AlGaN-Based UVB Light-Emitting Diodes
by Yi-Tsung Chang, Mu-Jen Lai, Rui-Sen Liu, Shu-Chang Wang, Xiong Zhang, Lin-Jun Zhang, Yu-Hsien Lin, Shiang-Fu Huang, Lung-Chien Chen and Ray-Ming Lin
Crystals 2022, 12(8), 1082; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12081082 - 01 Aug 2022
Cited by 3 | Viewed by 1724
Abstract
In this study, we found that the current droop (J-droop) in AlGaN-based UVB light-emitting diodes was more obvious at higher temperatures, despite both the main and parasitic peaks undergoing monotonic decreases in their intensity upon an increase in the temperature. The slower temperature [...] Read more.
In this study, we found that the current droop (J-droop) in AlGaN-based UVB light-emitting diodes was more obvious at higher temperatures, despite both the main and parasitic peaks undergoing monotonic decreases in their intensity upon an increase in the temperature. The slower temperature droop (T-droop) did not occur when the forward current was increased to temperatures greater than 298 K. After an aging time of 6000 h, the emission wavelengths did not undergo any obvious changes, while the intensity of the parasitic peak barely changed. Thus, the degradation in the light output power during long-term operation was not obviously correlated to the existence of the parasitic peak. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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8 pages, 2536 KiB  
Article
The Sensing Mechanism of InAlN/GaN HEMT
by Yanli Liu, Xiao He, Yan Dong, Su Fu, Yuhui Liu and Dunjun Chen
Crystals 2022, 12(3), 401; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12030401 - 16 Mar 2022
Cited by 3 | Viewed by 1864
Abstract
The sensing mechanism of InAlN/GaN high electron mobility transistors (HEMTs) is investigated systematically by numerical simulation and theoretical analysis. In detail, the influence of additional surface charge on device performance and the dependence of surface sensing properties on InAlN barrier thickness are studied. [...] Read more.
The sensing mechanism of InAlN/GaN high electron mobility transistors (HEMTs) is investigated systematically by numerical simulation and theoretical analysis. In detail, the influence of additional surface charge on device performance and the dependence of surface sensing properties on InAlN barrier thickness are studied. The results indicate that the saturation output drain current Idsat and two-dimensional electron gas (2DEG) concentration increase with the increase of positive surface charge density, which decrease with the increase of negative surface charge. The influence of negative surface charge on device performance is more remarkable than that of positive surface charge. Additionally, the modulation ability of surface charge on device performance increases with the decrease ofInAlN barrier thickness. The modulation of surface charge on device performance and the influence of barrier thickness on surface sensing sensitivity are mainly attributed to the variation of the energy band structure, surface potential and 2DEG concentration in the HEMT heterostructure. This work provides important support for structural optimization design of GaN-based HEMT sensors. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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Review

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23 pages, 4976 KiB  
Review
Recent Progress on AlGaN Based Deep Ultraviolet Light-Emitting Diodes below 250 nm
by Chunyue Zhang, Ke Jiang, Xiaojuan Sun and Dabing Li
Crystals 2022, 12(12), 1812; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12121812 - 13 Dec 2022
Cited by 4 | Viewed by 3300
Abstract
AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs), especially with a wavelength below 250 nm, have great application potential in the fields of sterilization and disinfection, gas sensing, and other aspects. However, with the decrease of emission wavelength, performance collapse occurs and the [...] Read more.
AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs), especially with a wavelength below 250 nm, have great application potential in the fields of sterilization and disinfection, gas sensing, and other aspects. However, with the decrease of emission wavelength, performance collapse occurs and the external quantum efficiencies (EQE) of sub-250 nm LEDs are usually below 1% for a long time. Low efficiencies are resulted from problem accumulation of all aspects, including n/p-type doping and contacts, carrier confinements and transports, light extraction, etc. To achieve high EQE of sub-250 nm LEDs, problems and solutions need to be discussed. In this paper, the research progress, development bottlenecks, and corresponding solutions of sub-250 nm LEDs are summarized and discussed in detail. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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42 pages, 16817 KiB  
Review
Reliability, Applications and Challenges of GaN HEMT Technology for Modern Power Devices: A Review
by Naeemul Islam, Mohamed Fauzi Packeer Mohamed, Muhammad Firdaus Akbar Jalaludin Khan, Shaili Falina, Hiroshi Kawarada and Mohd Syamsul
Crystals 2022, 12(11), 1581; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12111581 - 07 Nov 2022
Cited by 21 | Viewed by 11422
Abstract
A new generation of high-efficiency power devices is being developed using wide bandgap (WBG) semiconductors, like GaN and SiC, which are emerging as attractive alternatives to silicon. The recent interest in GaN has been piqued by its excellent material characteristics, including its high [...] Read more.
A new generation of high-efficiency power devices is being developed using wide bandgap (WBG) semiconductors, like GaN and SiC, which are emerging as attractive alternatives to silicon. The recent interest in GaN has been piqued by its excellent material characteristics, including its high critical electric field, high saturation velocity, high electron mobility, and outstanding thermal stability. Therefore, the superior performance is represented by GaN-based high electron mobility transistor (HEMT) devices. They can perform at higher currents, voltages, temperatures, and frequencies, making them suitable devices for the next generation of high-efficiency power converter applications, including electric vehicles, phone chargers, renewable energy, and data centers. Thus, this review article will provide a basic overview of the various technological and scientific elements of the current GaN HEMTs technology. First, the present advancements in the GaN market and its primary application areas are briefly summarized. After that, the GaN is compared with other devices, and the GaN HEMT device’s operational material properties with different heterostructures are discussed. Then, the normally-off GaN HEMT technology with their different types are considered, especially on the recessed gate metal insulator semiconductor high electron mobility transistor (MISHEMT) and p-GaN. Hereafter, this review also discusses the reliability concerns of the GaN HEMT which are caused by trap effects like a drain, gate lag, and current collapse with numerous types of degradation. Eventually, the breakdown voltage of the GaN HEMT with some challenges has been studied. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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18 pages, 6977 KiB  
Review
Surface Dispersion Suppression in High-Frequency GaN Devices
by Pengfei Zhu, Xianfeng Ni, Qian Fan and Xing Gu
Crystals 2022, 12(10), 1461; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101461 - 16 Oct 2022
Cited by 2 | Viewed by 2381
Abstract
GaN-based high electron mobility transistors (HEMTs) are shown to have excellent properties, showing themselves to perform well among the throng of solid-state power amplifiers. They are particularly promising candidates for next-generation mobile communication applications due to their high power density, frequency, and efficiency. [...] Read more.
GaN-based high electron mobility transistors (HEMTs) are shown to have excellent properties, showing themselves to perform well among the throng of solid-state power amplifiers. They are particularly promising candidates for next-generation mobile communication applications due to their high power density, frequency, and efficiency. However, the radio-frequency (RF) dispersion aroused by a high surface-state density inherent in nitrides causes the degradation of GaN devices’ performance and reliability. Although various dispersion suppression strategies have been proposed successively—including surface treatment, passivation, field plate, cap layer, and Si surface doping—outcomes were not satisfactory for devices with higher frequencies until the emergence of a novel N-polar deep recess (NPDR) structure broke this deadlock. This paper summarizes the generation of dispersion, several widespread dispersion containment approaches, and their bottlenecks under high frequencies. Subsequently, we highlight the NPDR structure as a potential substitute, evaluate its technical benefits, and review the continuous exertions in recent years. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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18 pages, 4420 KiB  
Review
Process of Au-Free Source/Drain Ohmic Contact to AlGaN/GaN HEMT
by Lin-Qing Zhang, Xiao-Li Wu, Wan-Qing Miao, Zhi-Yan Wu, Qian Xing and Peng-Fei Wang
Crystals 2022, 12(6), 826; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12060826 - 10 Jun 2022
Cited by 4 | Viewed by 5184
Abstract
AlGaN/GaN high electron mobility transistors (HEMTs) are regarded as promising candidates for a 5G communication system, which demands higher frequency and power. Source/drain ohmic contact is one of the key fabrication processes crucial to the device performance. Firstly, Au-contained metal stacks combined with [...] Read more.
AlGaN/GaN high electron mobility transistors (HEMTs) are regarded as promising candidates for a 5G communication system, which demands higher frequency and power. Source/drain ohmic contact is one of the key fabrication processes crucial to the device performance. Firstly, Au-contained metal stacks combined with RTA high-temperature ohmic contact schemes were presented and analyzed, including process conditions and contact formation mechanisms. Considering the issues with the Au-contained technique, the overview of a sequence of Au-free schemes is given and comprehensively discussed. In addition, in order to solve various problems caused by high-temperature conditions, novel annealing techniques including microwave annealing (MWA) and laser annealing (LA) were proposed to form Au-free low-temperature ohmic contact to AlGaN/GaN HEMT. The effects of the annealing method on surface morphology, gate leakage, dynamic on-resistance (RON), and other device characteristics are investigated and presented in this paper. By using a low-temperature annealing atmosphere or selective annealing method, gate-first Si-CMOS compatible AlGaN/GaN HEMT technology can be realized for high frequency and power application. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)
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