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p-type Cr2MnO4 with bandgap 3.01 eV was sputter deposited onto (2¯01) and (001) n-type or semi-insulating β-Ga2O3.The heterojunction of p-type CrMnO4 on n-type Ga2O3 is found to be type II, staggered gap, i.e., the band offsets are such that both the conduction and valence band edges of Ga2O3 are lower in energy than those of the Cr2MnO4. This creates a staggered band alignment, which can facilitate the separation of photogenerated electron-hole pairs. The valence band edge of Cr2MnO4 is higher than that of Ga2O3 by 1.82–1.93 eV depending on substrate orientation and doping, which means that holes in Cr2MnO4 would have a lower energy barrier to overcome to move into Ga2O3. Conversely, the conduction band edge of Cr2MnO4 is higher than that of Ga2O3 by 0.13–0.30 eV depending on substrate doping and orientation, which would create a barrier for electrons in Ga2O3 to move into Cr2MnO4. This heterojunction looks highly promising for p-n junction formation for advanced Ga2O3-based power rectifiers. 

Lateral Schottky or heterojunction rectifiers were irradiated with 10 MeV protons and neutrons. For proton irradiation, the forward current of both types of rectifiers decreased by approximately an order of magnitude, with a corresponding increase in on-state resistance. The resultant on/off ratio improved after irradiation because of the larger decrease in reverse current compared to forward current. Both types of rectifiers displayed a shift in forward current and RON curves to lower voltages after irradiation. This could be due to defects created by neutron irradiation introducing deep energy levels within the bandgap of AlN. These deep levels can trap charge carriers, reducing their mobility and increasing the on-state resistance. Transmission electron microscopy showed disorder created at the AlN/NiO interface by neutron irradiation. TCAD simulation was used to study the effects of irradiation with both protons and neutrons. The results confirmed that the irradiation caused a significant reduction in electron concentration and a small increase in the recombination rate. Neutron irradiation can also introduce interface states at the metal or oxide-semiconductor junction of the rectifier. These interface states can modify the effective Schottky barrier height, affecting the forward voltage drop and on-state resistance. 

Thermal annealing is commonly used in fabrication processing and/or performance enhancement of electronic and opto-electronic devices. In this study, we investigate an alternative approach, where high current density pulses are used instead of high temperature. The basic premise is that the electron wind force, resulting from the momentum loss of high-energy electrons at defect sites, is capable of mobilizing internal defects. The proposed technique is demonstrated on commercially available optoelectronic devices with two different initial conditions. The first study involved a thermally degraded edge-emitting laser diode. About 90% of the resulting increase in forward current was mitigated by the proposed annealing technique where very low duty cycle was used to suppress any temperature rise. The second study was more challenging, where a pristine vertical-cavity surface-emitting laser (VCSEL) was subjected to similar processing to see if the technique can enhance performance. Encouragingly, this treatment yielded a notable improvement of over 20% in the forward current. These findings underscore the potential of electropulsing as an efficient in-operando technique for damage recovery and performance enhancement in optoelectronic devices. 

Abstract In this study, we explore the rejuvenation of a Zener diode degraded by high electrical stress, leading to a leftward shift, and broadening of the Zener breakdown voltage knee, alongside a 57% reduction in forward current. We employed a non-thermal annealing method involving high-density electric pulses with short pulse width and low frequency. The annealing process took <30 s at near-ambient temperature. Raman spectroscopy supports the electrical characterization, showing enhancement in crystallinity to explain the restoration of the breakdown knee followed by improvement in forward current by ∼85%. 

High-power electronics, such as GaN high electron mobility transistors (HEMTs), are expected to perform reliably in high-temperature conditions. This study aims to gain an understanding of the microscopic origin of both material and device vulnerabilities to high temperatures by real-time monitoring of the onset of structural degradation under varying temperature conditions. This is achieved by operating GaN HEMT devices in situ inside a transmission electron microscope (TEM). Electron-transparent specimens are prepared from a bulk device and heated up to 800 °C. High-resolution TEM (HRTEM), scanning TEM (STEM), energy-dispersive x-ray spectroscopy (EDS), and geometric phase analysis (GPA) are performed to evaluate crystal quality, material diffusion, and strain propagation in the sample before and after heating. Gate contact area reduction is visible from 470 °C accompanied by Ni/Au intermixing near the gate/AlGaN interface. Elevated temperatures induce significant out-of-plane lattice expansion at the SiNx/GaN/AlGaN interface, as revealed by geometry-phase GPA strain maps, while in-plane strains remain relatively consistent. Exposure to temperatures exceeding 500 °C leads to almost two orders of magnitude increase in leakage current in bulk devices in this study, which complements the results from our TEM experiment. The findings of this study offer real-time visual insights into identifying the initial location of degradation and highlight the impact of temperature on the bulk device’s structure, electrical properties, and material degradation. 

Strain plays an important role in the performance and reliability of AlGaN/GaN high electron mobility transistors (HEMTs). However, the impact of strain on the performance of proton irradiated GaN HEMTs is yet unknown. In this study, we investigated the effects of strain relaxation on the properties of proton irradiated AlGaN/GaN HEMTs. Controlled strain relief is achieved locally using the substrate micro-trench technique. The strain relieved devices experienced a relatively smaller increase of strain after 5 MeV proton irradiation at a fluence of 5 × 1014 cm−2 compared to the non-strain relieved devices, i.e., the pristine devices. After proton irradiation, both pristine and strain relieved devices demonstrate a reduction of drain saturation current (Ids,sat), maximum transconductance (Gm), carrier density (ns), and mobility (μn). Depending on the bias conditions the pristine devices exhibit up to 32% reduction of Ids,sat, 38% reduction of Gm, 15% reduction of ns, and 48% reduction of μn values. In contrast, the strain relieved devices show only up to 13% reduction of Ids,sat, 11% reduction of Gm, 9% reduction of ns, and 30% reduction of μn values. In addition, the locally strain relieved devices show smaller positive shift of threshold voltage compared to the pristine devices after proton irradiation. The less detrimental impact of proton irradiation on the transport properties of strain relieved devices could be attributed to reduced point defect density producing lower trap center densities, and evolution of lower operation related stresses due to lower initial residual strain. 

Abstract Radiation susceptibility of electronic devices is commonly studied as a function of radiation energetics and device physics. Often overlooked is the presence or magnitude of the electrical field, which we hypothesize to play an influential role in low energy radiation. Accordingly, we present a comprehensive study of low-energy proton irradiation on gallium nitride high electron mobility transistors (HEMTs), turning the transistor ON or OFF during irradiation. Commercially available GaN HEMTs were exposed to 300 keV proton irradiation at fluences varying from 3.76 × 10¹²to 3.76 × 10¹⁴cm², and the electrical performance was evaluated in terms of forward saturation current, transconductance, and threshold voltage. The results demonstrate that the presence of an electrical field makes it more susceptible to proton irradiation. The decrease of 12.4% in forward saturation and 19% in transconductance at the lowest fluence in ON mode suggests that both carrier density and mobility are reduced after irradiation. Additionally, a positive shift in threshold voltage (0.32 V and 0.09 V in ON and OFF mode, respectively) indicates the generation of acceptor-like traps due to proton bombardment. high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy analysis reveal significant defects introduction and atom intermixing near AlGaN/GaN interfaces and within the GaN layer after the highest irradiation dose employed in this study. According toin-situRaman spectroscopy, defects caused by irradiation can lead to a rise in self-heating and a considerable increase in (∼750 times) thermoelastic stress in the GaN layer during device operation. The findings indicate device engineering or electrical biasing protocol must be employed to compensate for radiation-induced defects formed during proton irradiation to improve device durability and reliability. 

Forward bias hole injection from 10-nm-thick p-type nickel oxide layers into 10-μm-thick n-type gallium oxide in a vertical NiO/Ga2O3 p–n heterojunction leads to enhancement of photoresponse of more than a factor of 2 when measured from this junction. While it takes only 600 s to obtain such a pronounced increase in photoresponse, it persists for hours, indicating the feasibility of photovoltaic device performance control. The effect is ascribed to a charge injection-induced increase in minority carrier (hole) diffusion length (resulting in improved collection of photogenerated non-equilibrium carriers) in n-type β-Ga2O3 epitaxial layers due to trapping of injected charge (holes) on deep meta-stable levels in the material and the subsequent blocking of non-equilibrium carrier recombination through these levels. Suppressed recombination leads to increased non-equilibrium carrier lifetime, in turn determining a longer diffusion length and being the root-cause of the effect of charge injection. 

Radiation susceptibility of electronics has always been about probing electrical properties in either transient or time-accumulated phenomena. As the size and complexity of electronic chips or systems increase, detection of the most vulnerable regions becomes more time consuming and challenging. In this study, we hypothesize that localized mechanical stress, if overlapping electrically sensitive regions, can make electronic devices more susceptible to radiation. Accordingly, we develop an indirect technique to map mechanical and electrical hotspots to identify radiation-susceptible regions of the operational amplifier AD844 to ionizing radiation. Mechanical susceptibility is measured using pulsed thermal phase analysis via lock-in thermography and electrical biasing is used to identify electrically relevant regions. A composite score of electrical and mechanical sensitivity was constructed to serve as a metric for ionizing radiation susceptibility. Experimental results, compared against the literature, indicate effectiveness of the new technique in the rapid detection of radiation-vulnerable regions. The findings could be attractive for larger systems, for which traditional analysis would take —two to three orders of magnitude more time to complete. However, the indirect nature of the technique makes the study more approximate and in need for more consistency and validation efforts.