The ultraviolet photodetectors based on In:Ga2O3/p-GaN heterojunctions were fabricated by depositing an In:Ga2O3 thin film on a p-GaN substrate under different oxygen pressures using the pulsed laser deposition method. The devices exhibit typical self-powered behavior and a broad-spectrum response within the wavelength range of 250–345 nm. Under low oxygen pressure, the self-powered response peak of photodetectors with negative response current is mainly located at 345 nm, corresponding to the p-GaN layer. When the oxygen pressure exceeds 5 Pa, the response peak at 250 nm related to the In:Ga2O3 layer becomes the predominant peak, and the response current is positive. Studies demonstrate that the response peaks at 345 nm and 250 nm of the devices could be modulated by varying the applied bias voltage. The results indicate that, as the reverse bias increases, the response peak in the near ultraviolet region gradually decreases, while the response peak in the solar blind ultraviolet region gradually increases. The tunable photoresponse mechanism is attributed to the changes in the spatial-charge region and built-in electric field caused by devices prepared under different oxygen pressures and by varying the reverse bias applied to the devices.
Wang et al. (Thu,) studied this question.