Highly sensitive Ga₂O₃ MSM solar-blind UV photodetector with impact ionization gain

Abstract

In this study, a (400) crystal-oriented β-Ga2O3 thin film with a thickness of approximately 400 nm was grown on a c-plane sapphire substrate using atomic layer deposition. Schottky contact-type metal-semiconductor-metal solar-blind ultraviolet detectors with an Au/Ni/Ga2O3/Ni/Au structure were fabricated on the epitaxial thin films. The Schottky barrier height is about 1.1 eV. The device exhibited a high responsivity of up to 800 A/W, and a detectivity of 6 × 1014 Jones while maintaining a relatively fast response speed with a rise time of 4 ms and a fall time of 12 ms. The photo-to-dark current ratio was greater than 103, and the external quantum efficiency exceeded 103, indicating a significant gain in the device. Through the analysis of TCAD simulation and experimental results, it is determined that the impact ionization at the edge of the MSM electrode and channel contact is the main source of gain. Barrier tunneling effects and the photoconductive effect due to different carrier mobilities were not the primary reasons for the gain.