Hysteresis-free Ga2O3 solar-blind phototransistor modulated from photoconduction to photogating effect

High tunability of photoresponse characteristics under work conditions is desired for a single solar-blind photodetector to be applied in multifarious fields. Three-terminal metal–oxide–semiconductor field-effect phototransistors have shown excellent controllability of performance, but the hysteresis issue impedes their stable operation. In this work, the metal–semiconductor field-effect phototransistor based on the exfoliated Ga2O3 microflake and graphene thin film is demonstrated. The high-quality quasi-van der Waals interface between Ga2O3 and graphene eliminates the hysteresis issue and generates a subthreshold swing as low as 69.4 mV/dec. By regulating gate voltage (Vg), the dominated mechanism of photocurrent generation in the device can be tuned continuously from the fast photoconduction effect to photogating effect with high photogain. Accordingly, the responsivity, dark current, detectivity, rejection ratio, and decay time of the device can be well adjusted by the Vg. At Vg = −1 V and a source to drain voltage of 2 V, the device shows excellent performance with a responsivity of 2.82 × 103 A/W, a rejection ratio of 5.88 × 105, and a detectivity of 2.67 × 1015 Jones under 254 nm illumination. This work shows the possibility of realizing highly tunable solar-blind photodetectors to meet the requirements for different application fields by introducing gate voltage modulation.