We demonstrate superb large-area vertical β-Ga₂O₃ SBDs with a Schottky contact area of 1 × 1 mm² and obtain a high-efficiency DC–DC converter based on the device. The β-Ga₂O₃ SBD can obtain a forward current of 8 A with a forward voltage of 5 V, and has a reverse breakdown voltage of 612 V. The forward turn-on voltage (V_F) and the on-resistance (R_on) are 1.17 V and 0.46 Ω, respectively. The conversion efficiency of the β-Ga₂O₃ SBD-based DC–DC converter is 95.81%. This work indicates the great potential of Ga₂O₃ SBDs and relevant circuits in power electronic applications.

The self-heating effect severely limits device performance and reliability. Although some studies have revealed the heat distribution of β-Ga₂O₃ MOSFETs under biases, those devices all have small areas and have difficulty reflecting practical conditions. This work demonstrated a multi-finger β-Ga₂O₃ MOSFET with a maximum drain current of 0.5 A. Electrical characteristics were measured, and the heat dissipation of the device was investigated through infrared images. The relationship between device temperature and time/bias is analyzed.

A NiO/β-Ga₂O₃ heterojunction-gate field effect transistor (HJ-FET) is fabricated and its instability mechanisms are experimentally investigated under different gate stress voltage (V_G,s) and stress times (t_s). Two different degradation mechanisms of the devices under negative bias stress (NBS) are identified. At low V_G,s for a short t_s, NiO bulk traps trapping/de-trapping electrons are responsible for decrease/recovery of the leakage current, respectively. At higher V_G,s or long t_s, the device transfer characteristic curves and threshold voltage (V_TH) are almost permanently negatively shifted. This is because the interface dipoles are almost permanently ionized and neutralize the ionized charges in the space charge region (SCR) across the heterojunction interface, resulting in a narrowing SCR. This provides an important theoretical guide to study the reliability of NiO/β-Ga₂O₃ heterojunction devices in power electronic applications.

This work demonstrates high-performance NiO/β-Ga₂O₃ vertical heterojunction diodes (HJDs) with double-layer junction termination extension (DL-JTE) consisting of two p-typed NiO layers with varied lengths. The bottom 60-nm p-NiO layer fully covers the β-Ga₂O₃ wafer, while the geometry of the upper 60-nm p-NiO layer is 10 μm larger than the square anode electrode. Compared with a single-layer JTE, the electric field concentration is inhibited by double-layer JTE structure effectively, resulting in the breakdown voltage being improved from 2020 to 2830 V. Moreover, double p-typed NiO layers allow more holes into the Ga₂O₃ drift layer to reduce drift resistance. The specific on-resistance is reduced from 1.93 to 1.34 mΩ·cm². The device with DL-JTE shows a power figure-of-merit (PFOM) of 5.98 GW/cm², which is 2.8 times larger than that of the conventional single-layer JTE structure. These results indicate that the double-layer JTE structure provides a viable way of fabricating high-performance Ga₂O₃ HJDs.

In this work, W/β-Ga₂O₃ Schottky barrier diodes, prepared using a confined magnetic field-based sputtering method, were analyzed at different operation temperatures. Firstly, Schottky barrier height increased with increasing temperature from 100 to 300 K and reached 1.03 eV at room temperature. The ideality factor decreased with increasing temperature and it was higher than 2 at 100 K. This apparent high value was related to the tunneling effect. Secondly, the series and on-resistances decreased with increasing operation temperature. Finally, the interfacial dislocation was extracted from the tunneling current. A high dislocation density was found, which indicates the domination of tunneling through dislocation in the transport mechanism. These findings are evidently helpful in designing better performance devices.

Ultrawide band gap semiconductors are promising solar-blind ultraviolet (UV) photodetector materials due to their suitable bandgap, strong absorption and high sensitivity. Here, β-Ga₂O₃ microwires with high crystal quality and large size were grown by the chemical vapor deposition (CVD) method. The microwires reach up to 1 cm in length and were single crystalline with low defect density. Owing to its high crystal quality, a metal–semiconductor–metal photodetector fabricated from a Ga₂O₃ microwire showed a responsivity of 1.2 A/W at 240 nm with an ultrahigh UV/visible rejection ratio (R_peak/R_{400 nm}) of 5.8 × 10⁵, indicating that the device has excellent spectral selectivity. In addition, no obvious persistent photoconductivity was observed in the test. The rise and decay time constants of the device were 0.13 and 0.14 s, respectively. This work not only provides a growth method for high-quality Ga₂O₃ microwires, but also demonstrates the excellent performance of Ga₂O₃ microwires in solar-blind ultraviolet detection.