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1. 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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2. 10 kV GaN Power Diodes and Transistors with Performance beyond SiC Limit

   https://doi.org/10.1109/EDTM53872.2022.9797920  

   Zhang, Yuhao; Xiao, Ming; Ma, Yunwei; Cheng, Kai (March 2022, 10 kV GaN Power Diodes and Transistors with Performance beyond SiC Limit)

   Medium-voltage (MV) power electronic devices are widely used in renewable energy processing, electric grids, pulse power systems, etc. Current MV devices are mainly made of Si and SiC. This paper presents our recent efforts in developing a new generation of MV devices based on the multi-channel AlGaN/GaN platform and many new device designs involving charge balance, fin, and Cascode. The specific on-resistance of our 10 kV-class GaN Schottky barrier diodes and normally-OFF transistors is ~40 mΩ•cm 2 , rendering a Baliga’s figure of merit exceeding the 1-D unipolar SiC limits. We show the great promise of GaN in medium and high-voltage power applications. 

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3. Radiation Damage in the Ultra-Wide Bandgap Semiconductor Ga ₂ O ₃

   https://doi.org/10.1149/2162-8777/ac8bf7  

   Xia, Xinyi; Li, Jian-Sian; Sharma, Ribhu; Ren, Fan; Rasel, Md Abu; Stepanoff, Sergei; Al-Mamun, Nahid; Haque, Aman; Wolfe, Douglas E.; Modak, Sushrut; et al (September 2022, ECS Journal of Solid State Science and Technology)

   We present a review of the published experimental and simulation radiation damage results in Ga 2 O 3 . All of the polytypes of Ga 2 O 3 are expected to show similar radiation resistance as GaN and SiC, considering their average bond strengths. However, this is not enough to explain the orders of magnitude difference of the relative resistance to radiation damage of these materials compared to GaAs and dynamic annealing of defects is much more effective in Ga 2 O 3 . It is important to examine the effect of all types of radiation, given that Ga 2 O 3 devices will potentially be deployed both in space and terrestrial applications. Octahedral gallium monovacancies are the main defects produced under most radiation conditions because of the larger cross-section for interaction compared to oxygen vacancies. Proton irradiation introduces two main paramagnetic defects in Ga 2 O 3 , which are stable at room temperature. Charge carrier removal can be explained by Fermi-level pinning far from the conduction band minimum due to gallium interstitials (Ga i ), vacancies (V Ga ), and antisites (Ga O ). One of the most important parameters to establish is the carrier removal rate for each type of radiation, since this directly impacts the current in devices such as transistors or rectifiers. When compared to the displacement damage predicted by the Stopping and Range of Ions in Matter(SRIM) code, the carrier removal rates are generally much lower and take into account the electrical nature of the defects created. With few experimental or simulation studies on single event effects (SEE) in Ga 2 O 3 , it is apparent that while other wide bandgap semiconductors like SiC and GaN are robust against displacement damage and total ionizing dose, they display significant vulnerability to single event effects at high Linear Energy Transfer (LET) and at much lower biases than expected. We have analyzed the transient response of β -Ga 2 O 3 rectifiers to heavy-ion strikes via TCAD simulations. Using field metal rings improves the breakdown voltage and biasing those rings can help control the breakdown voltage. Such biased rings help in the removal of the charge deposited by the ion strike. 

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4. Photo-induced electron paramagnetic resonance: A means to identify defects and the defect level throughout the bandgap of ultrawide bandgap semiconductors

   https://doi.org/10.1063/5.0189934  

   Zvanut, M E; Mollik, Md_Shafiqul Islam; Siford, Mackenzie; Bhandari, Suman (January 2024, Applied Physics Letters)

   Ultrawide bandgap semiconductors (UWBGs) provide great promise for optical devices operating in the near to deep ultraviolet, and recently they have become a viable semiconducting material for high power electronics. From the power grid to electronic vehicles, the intention is to replace massively awkward components with the convenience of a solid state electronic “chip.” Unfortunately, the challenges faced by wide bandgap electronic materials, such as GaN and SiC, increase as the bandgap increases. A point defect, for example, can take on more charge states and energy configurations. This perspective describes a method to investigate the many charge states and their associated transitions—photo-induced electron paramagnetic resonance (photo-EPR) spectroscopy. Although not new to the study of defects in semiconductors, photo-EPR studies can probe the entire ultrawide bandgap given the appropriate light source for excitation. Examples provided here cover specific defects in UWBGs, AlN, and Ga2O3. The discussion also reminds us how the rapid pace of discovery surrounding this newest class of semiconductors is due, in part, to fundamental research studies of the past, some as far back as a century ago and some based on very different materials systems. 

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5. WIDE-BANDGAP SEMICONDUCTORS Gallium Nitride, GaN - Silicon Carbide, SiC

   Michael Haralambous, Chrysanthos Panayiotou (January 2022, WIDE-BANDGAP SEMICONDUCTORS)

   About the LASER-TEC Laser and Fiber Optics Educational Series This series was created for use in engineering technology programs such as electronics, photonics, laser electro-optics, etc. This series of publications has three goals in mind: 1) to create educational materials for areas of laser electro-optics technology in which no materials exist, 2) to work with industry to use, adapt, and enhance available industry-created materials, 3) to make these materials available at no cost which, in turn, would generate more accessible education to everyone (including technicians). The Laser and Fiber Optics Educational Series is available for free online at www.laser-tec.org. About Wide-Bandgap Semiconductors New semiconductors based on silicon carbide (SiC) and gallium nitride (GaN) are now commercially available, which has been instrumental in removing obstacles that legacy silicon bipolar and metal-oxide-semiconductor field-effect transistor (MOSFET) devices could not overcome. These new devices have superior power-handling abilities due to their better thermal properties, higher switching frequencies, and lower conduction losses. Collectively, these properties make wide-bandgap devices the preferred technology for high-power conversion applications with efficiencies approaching 99%. For this reason, this new technology must be introduced to existing curricula, preparing engineers and technicians to tackle today’s and tomorrow’s power electronics challenges. This module is intended for use in technical programs after coverage of basic semiconductor theory and discrete devices such as silicon diodes, bipolar junction, field effect, and MOSFET transistors. 

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