Gallium oxide (Ga2O3), 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 cm2 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-Ga2O3-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-Ga2O3 power device technologies. It will begins with a summary of the field and underlying semiconductor properties of Ga2O3, followed by a review of the growth methods of high-quality β-Ga2O3 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-Ga2O3 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.

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Flexible energy storage devices play a pivotal role in realizing the full potential of flexible electronics. This work presents high-performance, allsolid-state, flexible supercapacitors by employing an innovative multilevel porous graphite foam (MPG). MPGs exhibit superior properties, such as large specific surface area, high electric conductivity, low mass density, high loading efficiency of pseudocapacitive materials, and controlled corrugations for accommodating mechanical strains. When loaded with pseudocapacitive manganese oxide (Mn 3 O 4 ), the MPG/Mn 3 O 4 (MPGM) composites achieve a specific capacitance of 538 F g −1 (1 mV s −1 ) and 260 F g −1 (1 mV s −1 ) based on the mass of pure Mn 3 O 4 and entire electrode composite, respectively. Both are among the best of Mn 3 O 4 -based supercapacitors. The MPGM is mechanically robust and can go through 1000 mechanical bending cycles with only 1.5% change in electric resistance. When integrated as all-solid-state symmetric supercapacitors, they offer a full cell specific capacitance as high as 53 F g −1 based on the entire electrode and retain 80% of capacitance after 1000 continuous mechanical bending cycles. Furthermore, the all-solid-state flexible supercapacitors are incorporated with strain sensors into self-powered flexible devices for detection of both coarse and fine motions on human skins, i.e., those from finger bending and heart beating.

In this paper, we show that high-performance β-Ga2O3 hetero-junction barrier Schottky (HJBS) diodes with various β-Ga2O3 periodic fin widths of 1.5/3/5 μm are demonstrated with the incorporation of p-type NiOx. The β-Ga2O3 HJBS diode achieves a low specific on-resistance (Ron,sp) of 1.94 mΩ cm2 with a breakdown voltage of 1.34 kV at a β-Ga2O3 periodic fin width of 3 μm, translating to a direct-current Baliga's power figure of merit (PFOM) of 0.93 GW/cm2. In addition, we find that by shrinking the β-Ga2O3 width, the reverse leakage current is minimized due to the enhanced sidewall depletion effect from p-type NiOx. β-Ga2O3 HJBS diodes with p-type NiOx turn out to be an effective route for Ga2O3 power device technology by considering the high PFOM while maintaining a suppressed reverse leakage current.