Avalanche and surge robustness involve fundamental carrier dynamics under high electric field and current density. They are also prerequisites of any power device to survive common overvoltage and overcurrent stresses in power electronics applications such as electric vehicles, electricity grids, and renewable energy processing. Despite tremendous efforts to develop the next-generation power devices using emerging ultra-wide bandgap semiconductors, the lack of effective bipolar doping has been a daunting obstacle for achieving the necessary robustness in these devices. Here we report avalanche and surge robustness in a heterojunction formed between the ultra-wide bandgap n-type gallium oxide and the wide-bandgap p-type nickel oxide. Under 1500 V reverse bias, impact ionization initiates in gallium oxide, and the staggered band alignment favors efficient hole removal, enabling a high avalanche current over 50 A. Under forward bias, bipolar conductivity modulation enables the junction to survive over 50 A surge current. Moreover, the asymmetric carrier lifetime makes the high-level carrier injection dominant in nickel oxide, enabling a fast reverse recovery within 15 ns. This heterojunction breaks the fundamental trade-off between robustness and switching speed in conventional homojunctions and removes a key hurdle to advance ultra-wide bandgap semiconductor devices for power industrial applications.

In this work, we include the polarization effect within the AlGaN barrier into calculation of the near-surface electrical field $E_S$ underneath the Schottky contact metal which determines the field-dependent characteristics of reverse gate leakage current of AlGaN/GaN high electron mobility transistors. High-frequency capacitance-voltage measurement combined with electrostatic analysis is used to estimate $E_S$ as a function of reverse bias voltage. The resultant $\text{log}\left(I/E_S\right)$ versus $\sqrt{E_S}$ curves over a temperature range from 293 to 453 K agree well with the predicted model of Frenkel–Poole (FP) emission of electrons up to the conductive states of threading dislocations. Around zero bias, the reverse polarization-field-induced FP emission current is balanced by a forward defect-assisted tunneling current, both of which follow the same temperature dependent characteristics.

Ga ₂ O ₃ power diodes with high voltage/current ratings, superior dynamic performance, robust reliability, and potentially easy-to-implement are a vital milestone on the Ga ₂ O ₃ power electronics roadmap. In this letter, a better tradeoff between fast reverse-recovery and rugged surge-current capability has been demonstrated in NiO/Ga ₂ O ₃ p-n heterojunction diodes (HJDs). With the double-layered p-NiO design, the HJD exhibits superior electrostatic performances, including a high breakdown voltage of 1.37 kV, a forward current of 12.0 A with a low on-state resistance of 0.26 Ω, yielding a static Baliga's figure of merit (FOM) of 0.72 GW/cm ² . Meanwhile, the fast switching performance has been observed with a short reverse recovery time in nanosecond timescale (11 ns) under extreme switching conditions of di/dt up to 500 A/μs _. In particular, for a 9-mm ² HJD, a large surge current of 45 A has also been obtained in a 10-ms surge transient, thanks to the conductivity modulation effect. These results are comparable with those of the advanced commercial SiC SBDs and have significantly outperformed the past reported Ga ₂ O ₃ HJDs, fulfilling the enormous potential of Ga ₂ O ₃ in power applications.

The technical progress of Ga ₂ O ₃ power diodes is now stuck at a critical point where a lack of performance evaluation and reliability validation at the system-level applications seriously limits their further development and even future commercialization. In this letter, by implementing beveled-mesa NiO/Ga ₂ O ₃ p–n heterojunction diodes (HJDs) into a 500-W power factor correction (PFC) system circuit, high conversion efficiency of 98.5% with 100-min stable operating capability has been demonstrated. In particular, rugged reliability is validated after over 1 million times dynamic breakdown with a 1.2-kV peak overvoltage. Meanwhile, superior device performance is achieved, including a static breakdown voltage (BV) of 1.95 kV, a dynamic BV of 2.23 kV, a forward current of 20 A (2 kA/cm ² current density), and a differential specific on -resistance of 1.9 mΩ·cm ² . These results indicate that Ga ₂ O ₃ power HJDs are developing rapidly with their own advantages, presenting the enormous potential in high-efficiency, high-power, and high-reliability applications.

The electrical instability behaviors of a positive-gate-bias-stressed amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) are studied under monochromatic light illumination. It is found that as the wavelength of incident light reduces from 750 nm to 450 nm, the threshold voltage of the illuminated TFT shows a continuous negative shift, which is caused by photo-excitation of trapped electrons at the channel/dielectric interface. Meanwhile, an increase of the sub-threshold swing (SS) is observed when the illumination wavelength is below 625 nm (∼2.0 eV). The SS degradation is accompanied by a simultaneous increase of the field effect mobility (μ_FE) of the TFT, which then decreases at even shorter wavelength beyond 540 nm (∼2.3 eV). The variation of SS and μ_FE is explained by a physical model based on generation of singly ionized oxygen vacancies (V_o⁺) and double ionized oxygen vacancies (V_o²⁺) within the a-IGZO active layer by high energy photons, which would form trap states near the mid-gap and the conduction band edge, respectively.

In this paper, carrier transport and gain mechanisms are exploited in the $\beta $ -Ga ₂ O ₃ -based metal–semiconductor–metal photodetectors with Au back-to-back Schottky contacts. The resultant devices exhibit a low dark current of <10 pA at 10 V, a sustaining bias over 500 V without electric breakdown, a self-powered sensitivity with a UVC-to-visible rejection ratio over $10^{{3}}$ , and a photo-to-dark current ratio of 50 at 473 K, indicative of its strong operation capability at high temperature and in harsh environments. Temperature-dependent current–voltage features reveal that the dark reverse leakage is dominated by the thermionic field emission at low electric field and Poole–Frenkel emission from a deep trap level of 0.42 eV under the conduction band at high field, respectively. These negatively charged traps positioned below the Fermi level in the vicinity of Schottky interface capture photogenerated holes and reduce the barrier height upon illumination. The temperature- and bias-dependent photoresponse features are identified in physics that the photoconductive gain as well as slow response speed is originated from the change of barrier height due to trap repopulation.