Dependence of persistent photoconductivity on the thickness of β-Ga2O3 thin film photodetectors on c-plane sapphire via magnetron sputtering

Abstract

Abstract: β-Ga2O3 is a next-generation, ultra-wide bandgap semiconductor with intrinsic solar-blindness having the potential to replace Si for photodetection applications especially for the UV-C range. The material itself shows excellent photoconductive gain but is quite prone to the menace of the persistent photoconductivity, or the PPC. The fabricated devices become slower because of PPC and it also leads to reliability issues for photodetection logic. Herein, we report the dependence of the PPC effect on the different thickness of β-Ga2O3 thin film based solar-blind photodetectors. The polycrystalline films are grown on c-plane sapphire via RF magnetron sputtering at an elevated temperature of 500 °C. Optical bandgap of the films decreases with increasing thickness while their grain size increases. The oxygen-related defects studied using x-ray photoelectron spectroscopy are responsible for the observation of the enhanced PPC effect for the thinner films. The device performance is intimately connected with the quality of the thin film, its stoichiometry and the amount of oxygen defects present in the system. Better quality films with lower amount of oxygen vacancies show an improved performance with the least amount of PPC. This work shows that oxygen vacancies play an important role in determining the ultimate device performance and need to be engineered for high performance photodetectors.