Theoretical Study on the Role of Gating and Photoconduction on Ga2O3 Phototransistors

Gallium oxide (Ga2O3) phototransistors with low dark current and high ON-OFF ratio have been attracting considerable attention for UV-C light detection applications. However, the joint influence of photoconduction and gating on their photoresponse behaviors makes the photodetection mechanism experimentally ambiguous. Herein, a theoretical study on Ga2O3 phototransistors is performed with technology computer-aided design (TCAD) Silvaco software to reveal the role of gate bias and external UV-C light illumination on their electrical characteristics. The analyses on the transfer curves before and after 250-nm light illumination figure out that the responsivity increases and then decreases with the gate bias, and the gate bias required to achieve the maximum responsivity increases with Ga2O3 thickness. Interestingly, under weak light irradiation, the current density of Ga2O3 phototransistors is found to be obviously enhanced by the gate bias owing to the effective separation of photo-generated electron-hole pairs. However, this gating effect is weakened upon strong UV-C light illumination. Our theoretical work clarifies the synergism and competition relationships between photoconduction and gating effects and offers a reference for the design of high-performance Ga2O3 phototransistors.