Balanced performance for β-Ga2O3 solar blind photodetectors: The role of oxygen vacancies

Gallium oxide (Ga2O3) is a natural candidate material for next-generation solar-blind photodetectors (PDs). At present, it remains challenging to tune a balanced performance with high responsivity and fast response speed for the metal-semiconductor-metal (MSM) PDs due to the specific internal gain and persistent photoconductivity (PPC) effect. Herein, a series of amorphous and β-phase Ga2O3 films with ultra-high transmittance (>95%) in the near ultraviolet–visible region are obtained by combing with magnetron sputtering and post-annealing. Then, we fabricated MSM solar-blind photodetectors based on amorphous and β-phase Ga2O3 films with different post-annealing temperatures. The results show that the amorphous Ga2O3 PD has higher responsivity (R), detectivity (D*) and external quantum efficiency (EQE), but its response speed is slow, and photo-to-dark current ratio (PDCR) and rejection ratio (R254/R365) are relatively low. In contrast, the devices fabricated based on high temperature annealed β-Ga2O3 films display faster response speed, higher PDCR and R254/R365, but lower R, D* and EQE. It is demonstrated that oxygen vacancies dominate the internal gain and PPC of the device, the concentration of which in turn determines the performance of the device. A β-Ga2O3 photodetector presented more balanced performance is obtained by properly controlling the concentration of oxygen vacancies.