Power electronic devices are of great importance in modern society. After decades of development, Si power devices have approached their material limits with only incremental improvements and large conversion losses. As the demand for electronic components with high efficiency dramatically increasing, new materials are needed for power device fabrication. Beta-phase gallium oxide, an ultra-wide bandgap semiconductor, has been considered as a promising candidate, and various β-Ga₂O₃ power devices with high breakdown voltages have been demonstrated. However, the realization of enhancement-mode (E-mode) β-Ga₂O₃ field-effect transistors (FETs) is still challenging, which is a critical problem for a myriad of power electronic applications. Recently, researchers have made some progress on E-mode β-Ga₂O₃ FETs via various methods, and several novel structures have been fabricated. This article gives a review of the material growth, devices and properties of these E-mode β-Ga₂O₃ FETs. The key challenges and future directions in E-mode β-Ga₂O₃ FETs are also discussed.

GaN has been widely used in the fabrication of ultraviolet photodetectors because of its outstanding properties. In this paper, we report a graphene–GaN nanorod heterostructure photodetector with fast photoresponse in the UV range. GaN nanorods were fabricated by a combination mode of dry etching and wet etching. Furthermore, a graphene–GaN nanorod heterostructure ultraviolet detector was fabricated and its photoelectric properties were measured. The device exhibits a fast photoresponse in the UV range. The rising time and falling time of the transient response were 13 and 8 ms, respectively. A high photovoltaic responsivity up to 13.9 A/W and external quantum efficiency up to 479% were realized at the UV range. The specific detectivity D^* = 1.44 × 10¹⁰ Jones was obtained at –1 V bias in ambient conditions. The spectral response was measured and the highest response was observed at the 360 nm band.

A monolithic integrated ultraviolet-infrared (UV-IR) dual-color photodetector based on graphene/GaN heterojunction was fabricated by vertically integrating a GaN nanowire array on a silicon substrate with monolayer graphene. The device detects UV and IR lights by different mechanisms. The UV detection is accomplished by the forbidden band absorption of GaN, and the IR detection is realized by the free electron absorption of graphene. At peak wavelengths of 360 nm and 1540 nm, the detector has responsivities up to 6.93 A/W and 0.11 A/W, detection efficiencies of 1.23 × 10¹² cm·Hz^1/2 ·W^-1 and 1.88 × 10¹⁰ cm·Hz^1/2 ·W^-1, respectively, and a short response time of less than 3 ms.