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 beta-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 beta-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 beta-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 beta-Ga2O3 photodetector presented more balanced performance is obtained by properly controlling the concentration of oxygen vacancies.

Automated summary

Balanced performance of Ga2O3 photodetectors can be achieved by controlling the concentration of oxygen vacancies, with beta-Ga2O3 showing faster response speed and higher PDCR and rejection ratio, while amorphous Ga2O3 exhibiting higher responsivity, detectivity and external quantum efficiency.