Oxygen vacancies modulating the photodetector performances in ε-Ga2O3 thin films

Abstract

By acting as the trapping centers during charge carrier transfer, oxygen vacancy (VO) plays a critical role in oxide photoelectric devices. Herein, a post-annealing method was introduced to perfect the photodetection performances of ε-Ga₂O₃ photodetectors (PDs) by improving the film quality and modulating the V_O defect concentration. The native oxygen-deficient ε-Ga₂O₃ epitaxial films fabricated via metal–organic chemical vapor deposition become highly dense and V_O-less after oxidation annealing, leading to an enhanced performance, while they become V_O-rich after reduction annealing to depress the PD property. Compared with the pristine PD, the crucial parameters of the devices with a lower V_O concentration have been improved by 1–6 magnitude with a high photo-to-dark current ratio of 1.06 × 10⁸, a large responsivity of 1.368 A W⁻¹, an excellent detectivity of 9.13 × 10¹⁴ Jones, a superior linear dynamic range of 176.7 dB and an outstanding external quantum efficiency of 666.5% and a record-high rejection ratio (R₂₄₀/R₄₀₀) of 1.80 × 10⁷. As the V_O defect is commonly ubiquitous in oxide materials, our investigation of regulating the V_O concentrations in ε-Ga₂O₃ and then exerting influences on the PD capabilities will provide principles for designing high-performance photoelectric devices.