Beta-phase gallium oxide (β-Ga₂O₃) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power electronics and deep ultraviolet optoelectronics. Key advantages of β-Ga₂O₃ include the availability of large-size single-crystal bulk native substrates produced from melt and the precise control of n-type doping during both bulk growth and thin-film epitaxy. A comprehensive understanding of the fundamental growth processes, control parameters, and underlying mechanisms is essential to enable scalable manufacturing of high-performance epitaxial structures. This review highlights recent advancements in the epitaxial growth of β-Ga₂O₃ through various techniques, including Molecular Beam Epitaxy (MBE), Metal-Organic Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVPE), Mist Chemical Vapor Deposition (Mist CVD), Pulsed Laser Deposition (PLD), and Low-Pressure Chemical Vapor Deposition (LPCVD). This review concentrates on the progress of Ga₂O₃ growth in achieving high growth rates, low defect densities, excellent crystalline quality, and high carrier mobilities through different approaches. It aims to advance the development of device-grade epitaxial Ga₂O₃ thin films and serves as a crucial resource for researchers and engineers focused on UWBG semiconductors and the future of power electronics.

We demonstrate threshold switching behaviors with working temperatures up to 500 $^{\circ}$ C based on GaN vertical p-n diodes, and these devices survived a passive test in a simulated Venus environment (460 $^{\circ}$ C, 94 bar, CO $_{\text{2}}$ gas flow) for ten days. This is realized via interface engineering through an etch-then-regrow process combination with a Ga $_{\text{2}}$ O $_{\text{3}}$ interlayer. It is hypothesized the traps in the interfacial layer can form/rupture a conductive path by trapping/detrapping electrons/holes, which are responsible for the observed threshold switching behaviors. To the best of our knowledge, this is the first demonstration of two-terminal threshold-switching memory devices under such high temperatures. These results can serve as a critical reference for the future development of GaN-based memory devices for harsh environment applications.

In this work, we demonstrate the high performance of β-Ga2O3 metal–insulator–semiconductor (MIS) diodes. An ultrathin boron nitride (BN) interlayer is directly grown on the Ga2O3 substrate by pulsed laser deposition. X-ray photoelectron spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy confirm the existence of a 2.8 nm BN interlayer. Remarkably, with the insertion of the ultrathin BN layer, the breakdown voltage is improved from 732 V for Ga2O3 Schottky barrier diodes to 1035 V for Ga2O3 MIS diodes owing to the passivated surface-related defects and reduced reverse leakage currents. Our approach shows a promising way to improve the breakdown performance of Ga2O3-based devices for next-generation high-power electronics.

In this Letter, low-temperature (400 °C) chemical vapor deposition-grown boron nitride (BN) was investigated as the gate dielectric for AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) on a Si substrate. Comprehensive characterizations using x-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, atomic force microscope, high-resolution transmission electron microscopy, and time-of-flight secondary ion mass spectrometry were conducted to analyze the deposited BN dielectric. Compared with conventional Schottky-gate HEMTs, the MISHEMTs exhibited significantly enhanced performance with 3 orders of magnitude lower reverse gate leakage current, a lower off-state current of 1 × 10−7 mA/mm, a higher on/off current ratio of 108, and lower on-resistance of 5.40 Ω mm. The frequency-dependent conductance measurement was performed to analyze the BN/HEMT interface, unveiling a low interface trap state density (Dit) on the order of 5 × 1011–6 × 1011 cm−2 eV−1. This work shows the effectiveness of low-temperature BN dielectrics and their potential for advancing GaN MISHEMTs toward high-performance power and RF electronics applications.

This Letter reports the performance of vertical GaN-on-GaN p–n diodes with etch-then-regrown p-GaN after exposure to a simulated Venus environment (460 °C, ∼94 bar, containing CO2/N2/SO2 etc., atmosphere) for over 10 days, and compared them to the performance of GaN p–n diodes without the etch-then-regrow process. After the above-mentioned Venus test, temperature-dependent I–V and microscopy investigation were conducted to study the robustness of etch-then-regrow p-GaN and vertical GaN p–n diodes under harsh environments and operation up to 500 °C. p-electrode degradation is found to be the main issue of the device's performance. This is the highest temperature at which such characterization has been conducted for vertical GaN p–n diodes, therefore establishing a critical reference for the development of p-GaN regrown and vertical GaN-based electronics for extreme environments.

With the increasing power density of GaN-based power devices, the self-heating effect has become a significant bottleneck, impacting device reliability and performance, which makes effective thermal management essential. Hexagonal boron nitride (h-BN), with its high thermal conductivity and excellent electrical insulation, offers a promising solution for heat dissipation. In this Letter, we demonstrate that the transferred low-pressure chemical vapor deposition-grown h-BN effectively mitigates self-heating in AlGaN/gallium nitride high electron mobility transistors. All 12 tested devices showed increased current after BN transfer. The average current density in the saturation region improved from 819 to 924 mA/mm, and the current retention rose from 89% to 98%. Thermo-reflectance measurements revealed a significant reduction in channel temperature from 179 to 115 °C under a power density of 21 W/mm. The improvement is attributed to the high in-plane thermal conductivity of h-BN, which is proven by the hotspot models. This approach shows promise as a practical method to reduce self-heating and enhance the thermal reliability of GaN-based power transistors.