The role of oxygen vacancies in Ga2O3-based solar-blind photodetectors

Gallium oxide (Ga2O3) with an ultrawide bandgap, is a promising and inherent material for solar-blind photodetectors (SBPDs). However, it remains a challenge to achieve a photodetector with large responsivity and fast response speed owing to the presence of intrinsic oxygen vacancies (VO) in the Ga2O3 films. Here, the annealing and doping engineering is proposed to break the compromise between the responsivity and response speed, based on the low-cost method for annealing nitrogen-doped Ga2O3 films with various concentrations of VO in Ar, O2, and N2 atmospheres. The mechanism of regulating VO in the nitrogen-doped Ga2O3 films under various annealing atmospheres has been clarified first. The influence of concentrations of VO in pristine films and annealing atmospheres on the photoelectric properties of annealed films was analyzed systematically. The nitrogen-doping, recrystallization, and the appropriate concentration of VO in pristine Ga2O3 films are favorable factors for optimizing the properties of the post-annealing Ga2O3 films. The photodetectors based on annealing and doping engineering exhibit impressive characteristics with high photo-to-dark current ratios (PDCRs) of 2.6 x 107, large rejection ratio of R254 /R365 = 1.0 x 106, especially the faster response speed of 0.359/0.110 s, 9.8 times higher R254, and 6.34 x 102 times lower Idark than pristine films. The regulation of VO via doping and annealing methods can provide an effective strategy for low-cost high-performance Ga2O3-based SBPDs.