A review of Ga2O3 deep-ultraviolet metal–semiconductor Schottky photodiodes

Abstract

Abstract Deep-ultraviolet (DUV) photodetectors are fundamental building blocks in many solid-state DUV optoelectronics, and their success relies on continuous innovations in semiconductor materials and the physics of device structures. Overcoming the technological obstacles in narrow-bandgap silicon-based optoelectronics (photodetectors and photonics), the wide-bandgap semiconductor attracted much attention when used in a DUV photodetector, among which gallium oxide is a typical representative material benefiting from its promising physical and chemical properties in nature, especially for its energy bandgap around 4.5–5.2 eV for its five phases (α, β, γ, ϵ, and δ). It responds to DUV light irradiation without the need to adjust the component in compounds and/or add external optical instruments, as with some compound semiconductors (Al x Ga1−x N, Mg x Zn1−x O, etc.) According to literature reports on Ga2O3-based photodetectors, the device morphology includes a metal–semiconductor–metal photodetector, homojunction or heterojunction photodetector, phototransistor, and Schottky photodiode. Notably, the Schottky photodiode with a rectified Schottky junction has the advantages of easy fabrication, fast photoresponse, less high-temperature diffusion, low dark current, high detectivity, and self-powered operation; however, its weaknesses include its thin depletion layer and low barrier at the metal–semiconductor interface. Therefore, in this concise literature review article, the recent progress of Ga2O3-based Schottky photodiodes is discussed in order to show some suggestions on the choice of Schottky metal, interfacial barrier modulation, space electric field adjustment, energy band engineering, and photodetection performance improvement, with the aim of promoting the further development of DUV photodetection in the near future.