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1. GaN/A!N Schottky-gate p-channel HFETs with InGaN contacts and 100 mA/mm on-current

   Bader B.J., Chaudhuri (January 2019, IED)

   High performance wide bandgap p-channel devices which can be monolithically integrated with established wide-bandgap n-channel devices are broadly desirable to expand the design topologies available in power/RF electronics. This work advances the GaN-onAIN platform as the most promising p-channel contender to enable wide-bandgap complementary electronics. Toward that end, a new generation of GaN-on-AIN p-channel HFET's is fabricated with on-currents exceeding 100mA/mm at room temperature under moderate drain bias. Key fabrication ingredients to this success are discussed, low-temperature characterization is shared, and new results benchmarked against the broader literature. 

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2. Radiation damage in GaN/AlGaN and SiC electronic and photonic devices

   https://doi.org/10.1116/6.0002628  

   Pearton, S. J.; Xia, Xinyi; Ren, Fan; Rasel, Md Abu; Stepanoff, Sergei; Al-Mamun, Nahid; Haque, Aman; Wolfe, Douglas E. (May 2023, Journal of Vacuum Science & Technology B)

   The wide bandgap semiconductors SiC and GaN are commercialized for power electronics and for visible to UV light-emitting diodes in the case of the GaN/InGaN/AlGaN materials system. For power electronics applications, SiC MOSFETs (metal–oxide–semiconductor field effect transistors) and rectifiers and GaN/AlGaN HEMTs and vertical rectifiers provide more efficient switching at high-power levels than do Si devices and are now being used in electric vehicles and their charging infrastructure. These devices also have applications in more electric aircraft and space missions where high temperatures and extreme environments are involved. In this review, their inherent radiation hardness, defined as the tolerance to total doses, is compared to Si devices. This is higher for the wide bandgap semiconductors, due in part to their larger threshold energies for creating defects (atomic bond strength) and more importantly due to their high rates of defect recombination. However, it is now increasingly recognized that heavy-ion-induced catastrophic single-event burnout in SiC and GaN power devices commonly occurs at voltages ∼50% of the rated values. The onset of ion-induced leakage occurs above critical power dissipation within the epitaxial regions at high linear energy transfer rates and high applied biases. The amount of power dissipated along the ion track determines the extent of the leakage current degradation. The net result is the carriers produced along the ion track undergo impact ionization and thermal runaway. Light-emitting devices do not suffer from this mechanism since they are forward-biased. Strain has also recently been identified as a parameter that affects radiation susceptibility of the wide bandgap devices. 

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3. Radiation damage in GaN/AlGaN and SiC electronic and photonic devices

   S. J. Pearton; Xinyi Xia; Fan Ren; Md Abu Jafar Rasel; Sergei Stepanoff; Nahid Al-Mamun; Aman Haque; Douglas E. Wolfe (May 2023, Journal of vacuum science and technology B Nanotechnology microelectronics)

   The wide bandgap semiconductors SiC and GaN are commercialized for power electronics and for visible to UV light-emitting diodes in the case of the GaN/InGaN/AlGaN materials system. For power electronics applications, SiC MOSFETs (metal–oxide–semiconductor field effect transistors) and rectifiers and GaN/AlGaN HEMTs and vertical rectifiers provide more efficient switching at high-power levels than do Si devices and are now being used in electric vehicles and their charging infrastructure. These devices also have applications in more electric aircraft and space missions where high temperatures and extreme environments are involved. In this review, their inherent radiation hardness, defined as the tolerance to total doses, is compared to Si devices. This is higher for the wide bandgap semiconductors, due in part to their larger threshold energies for creating defects (atomic bond strength) and more importantly due to their high rates of defect recombination. However, it is now increasingly recognized that heavy-ion-induced catastrophic single-event burnout in SiC and GaN power devices commonly occurs at voltages ∼50% of the rated values. The onset of ion-induced leakage occurs above critical power dissipation within the epitaxial regions at high linear energy transfer rates and high applied biases. The amount of power dissipated along the ion track determines the extent of the leakage current degradation. The net result is the carriers produced along the ion track undergo impact ionization and thermal runaway. Light-emitting devices do not suffer from this mechanism since they are forward-biased. Strain has also recently been identified as a parameter that affects radiation susceptibility of the wide bandgap devices. 

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4. Properties and device performance of BN thin films grown on GaN by pulsed laser deposition

   https://doi.org/10.1063/5.0092356  

   Biswas, Abhijit; Xu, Mingfei; Fu, Kai; Zhou, Jingan; Xu, Rui; Puthirath, Anand B.; Hachtel, Jordan A.; Li, Chenxi; Iyengar, Sathvik Ajay; Kannan, Harikishan; et al (September 2022, Applied Physics Letters)

   Wide and ultrawide-bandgap semiconductors lie at the heart of next-generation high-power, high-frequency electronics. Here, we report the growth of ultrawide-bandgap boron nitride (BN) thin films on wide-bandgap gallium nitride (GaN) by pulsed laser deposition. Comprehensive spectroscopic (core level and valence band x-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Raman) and microscopic (atomic force microscopy and scanning transmission electron microscopy) characterizations confirm the growth of BN thin films on GaN. Optically, we observed that the BN/GaN heterostructure is second-harmonic generation active. Moreover, we fabricated the BN/GaN heterostructure-based Schottky diode that demonstrates rectifying characteristics, lower turn-on voltage, and an improved breakdown capability (∼234 V) as compared to GaN (∼168 V), owing to the higher breakdown electrical field of BN. Our approach is an early step toward bridging the gap between wide and ultrawide-bandgap materials for potential optoelectronics as well as next-generation high-power electronics. 

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5. Thermal analysis of an α-Ga2O3 MOSFET using micro-Raman spectroscopy

   https://doi.org/10.1063/5.0164095  

   Karim, Anwarul; Song, Yiwen; Shoemaker, Daniel C; Jeon, Dae-Woo; Park, Ji-Hyeon; Mun, Jae Kyoung; Lee, Hun Ki; Choi, Sukwon (November 2023, Applied Physics Letters)

   The ultra-wide bandgap (UWBG) energy (∼5.4 eV) of α-phase Ga2O3 offers the potential to achieve higher power switching performance and efficiency than today's power electronic devices. However, a major challenge to the development of the α-Ga2O3 power electronics is overheating, which can degrade the device performance and cause reliability issues. In this study, thermal characterization of an α-Ga2O3 MOSFET was performed using micro-Raman thermometry to understand the device self-heating behavior. The α-Ga2O3 MOSFET exhibits a channel temperature rise that is more than two times higher than that of a GaN high electron mobility transistor (HEMT). This is mainly because of the low thermal conductivity of α-Ga2O3 (11.9 ± 1.0 W/mK at room temperature), which was determined via laser-based pump-probe experiments. A hypothetical device structure was constructed via simulation that transfer-bonds the α-Ga2O3 epitaxial structure over a high thermal conductivity substrate. Modeling results suggest that the device thermal resistance can be reduced to a level comparable to or even better than those of today's GaN HEMTs using this strategy combined with thinning of the α-Ga2O3 buffer layer. The outcomes of this work suggest that device-level thermal management is essential to the successful deployment of UWBG α-Ga2O3 devices. 

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