Influence of Finely Tuning Power and Oxygen Flux Ratio on Optoelectronic Properties of Sputtered Amorphous Gallium Oxide Thin Films

Amorphous gallium oxide (a-GaOx) thin films for use as a solar-bind photodetector material have been prepared by radio-frequency magnetron sputtering technique on quartzes. The influence of sputtering power and oxygen flux ratio on optical and electrical properties of a-GaOx thin films and photodetectors were systematically investigated. The optical bandgap, band tail states, and work function are affected by a combination of oxygen vacancies and structure disorder. Decreasing sputtering power and increasing oxygen flux ratio reduce the oxygen deficiencies of these materials. The structure order could monotonically increase with decreasing oxygen flux ratio and first increase and then decrease with increasing sputtering power. The photoelectrical properties are sensitive to the deposition parameters. The photodetectors based on a-GaOx deposited with 210 W and 0.4% O2 flux ratio has the highest photo current and lowest dark current due to the moderate defect density and contact barrier height. Although the photo current is only less than 100 μA, the dark current is as low as a few tenth pA resulting in the largest PDCR of about 106.