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

Abstract

Gallium oxide (Ga 2 O 3 ) 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 Ga 2 O 3 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 Ga 2 O 3 films with different post-annealing temperatures. The results show that the amorphous Ga 2 O 3 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 (R 254 /R 365 ) are relatively low. In contrast, the devices fabricated based on high temperature annealed β-Ga 2 O 3 films display faster response speed, higher PDCR and R 254 /R 365 , 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-Ga 2 O 3 photodetector presented more balanced performance is obtained by properly controlling the concentration of oxygen vacancies. • Highly transparent Ga 2 O 3 thin films with a transmittance of >95% are prepared. • Changing the annealing temperature can effectively control the oxygen vacancies. • Oxygen vacancies determine the performance of the Ga 2 O 3 MSM photodetectors. • A β-Ga 2 O 3 photodetector presented more balanced performance can be realized.