Gallium oxide (Ga ₂ O ₃ ), an emerging ultra-wide-bandgap semiconductor, has the desirable properties of a large bandgap of 4.6–4.9 eV, an estimated critical breakdown field of 8 MV cm ⁻¹ , decent electron mobility of 250 cm ² V s ⁻¹ and high theoretical Baliga figures of merit (BFOMs) of around 3000. Bolstered by their capability of an economical growth technique for high-quality bulk substrate, β -Ga ₂ O ₃ -based materials and devices have been highly sought after in recent years for power electronics and solar-blind ultraviolet photodetectors. This article reviews the most recent advances in β -Ga ₂ O ₃ power device technologies. It will begins with a summary of the field and underlying semiconductor properties of Ga ₂ O ₃ , followed by a review of the growth methods of high-quality β -Ga ₂ O ₃ bulk substrates and epitaxial thin films. Then, brief perspectives on the advanced technologies and measurements in terms of ohmic contact and interface state are provided. Furthermore, some state-of-the-art β -Ga ₂ O ₃ photoelectronic devices, power devices and radiofrequency devices with distinguished performance are fully described and discussed. Some solutions to alleviating challenging issues, including the difficulty in p-type doping, low thermal conductivity and low mobility, are also presented and explored.

In this work, we have demonstrated normally-off β-Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET) with the ferroelectric charge storage gate stack structure. Saturation currents of 18.3 and 16.0 mA/mm were achieved in Depletion (D-) and Enhancement (E-) mode device, respectively, which shows negligible current reduction. Steep subthreshold swing (SS) of 72 mV/dec and breakdown voltage of 670 V were also obtained in the E-mode MOSFET. Furthermore, after gate stess test of 10 V for 105 s was performed. The threshold voltage (VTH) shift was 26.5 %. These electrical characteristics of the E-mode β-Ga2O3 MOSFET shows the great potential for future power switch application.

In this article, we have carried out a comprehensive study on the wireless power transfer (WPT) concept from the rectifier circuit construction and state-of-art GaN Schottky barrier diode (SBD) device technology to the WPT system demonstration. Benefited from the wide bandgap, high mobility, and saturation velocity of the gallium nitride (GaN) two-dimensional electron gas, engineered lateral GaN SBD with low turn- on voltage ( V _on ) of 0.47 V, on -resistance ( R _on ) of 4 Ω, breakdown voltage of 170 V, and junction capacitance $(C_{j})$ of 0.32 pF at 0 V bias are achieved, which satisfy the fundamental requirements for microwave power rectification. After incorporating the high-performance GaN SBD into the optimized rectifier circuit, high radio frequency (RF)/dc conversion efficiency of 79% is achieved, and the input power of per single GaN SBD is increased by 10X when compared with that of a commercially available silicon (Si) SBD at the same efficiency of 50% and frequency of 2.45 GHz. Based on the rectifier circuit, a microwave power transfer system is constructed with 400 light emitting diodes lighted up, verifying the great promise of adopting high-power GaN SBD for the wireless high-power transfer as an alternative energy-harvesting technique for future WPT application.

In this letter, we demonstrate a high-performance lateral AlGaN/GaN Schottky barrier diode (SBD) using an 80-nm thick GaN cap layer as the passivation layer and a low work-function tungsten (W) layer as the anode. A low turn-on voltage ( ${V}_{ON}$ ) of 0.38 V and a high breakdown voltage of 2.08 kV are obtained at the same time. Additionally, the normalized dynamic on-resistance ( ${R}_{ON,dyn}$ ) becomes only a factor of 1.13 higher than the static on-resistance ( ${R}_{ON}$ ) after a 10-s-long bias test at 900 V. Also owing to the impressively stability of ${R}_{ON,dyn}$ and ${V}_{ON}$ under long-duration stress, these lateral GaN SBDs with a thick GaN cap layer show a great potential for the next-generation of power electronic devices.

In this letter, a high-performance GaN quasi-vertical Schottky barrier diode (SBD) is demonstrated via oxygen plasma termination. A specific on-resistance of 0.2 mΩ·cm ² , turn-on voltage of 0.71 V, and breakdown voltage of 193 V are achieved with a GaN SBD of 1.3μm drift layer. The average breakdown electric field is calculated to be about 1.48 MV/cm, which is much higher than the state-of-art value for GaN vertical SBDs. The temperature-dependent forward and reverse I-V characteristics confirm the high-temperature stability of the oxygen plasma treated SBDs. X-ray spectroscopy and Kelvin Probe Force Microscopy reveal that the surface potential is increased after the oxygen plasma treatment, which results in the suppression of the leakage current and improvement of the breakdown electric field.