Photogain-Enhanced Signal-to-Noise Performance of a Polycrystalline Sn:Ga2O3 UV Detector via Impurity-Level Transition and Multiple Carrier Transport

In this work, a deep-UV photodetector based on a Sn-doped Ga2O3 (Sn:Ga2O3) thin film grown by mist chemical vapor deposition (mist-CVD) technology on an α-Al2O3 substrate is introduced. This feasible and cheap mist-CVD method contributed to the preparation of a Sn:Ga2O3 thin film. It was found that the device exhibits a dark current as low as 10 pA and a photocurrent of 2.96 μA at −6 V, with a photo-to-dark current ratio of 2.96 × 105, an external quantum efficiency of 245.79%, and a photoresponsivity of 0.72 A/W. The higher performance compared to that of the Ga2O3 thin film without the Sn dopant is because of the introduced impurity energy level, which is higher than the Fermi level. Thus, the electrons at the valence band arrive more easily at the impurity energy level by traversing the Fermi level to obtain electrons at the conduction band. Together with multiple carrier transport, the detector displayed a photoconductive gain greater than 100%. The results could enhance the signal-to-noise performance as a key parameter of photodetectors.