Preparation of β-Ga2O3 films on off-angled sapphire substrates and solar-blind ultraviolet photodetectors

Abstract β -Ga 2 O 3 films have been prepared on (0001) sapphire substrates with different off-axis angles toward $?> < 11 2 ˉ 0 > by sol – gel method and the solar-blind ultraviolet photodetectors (PDs) with metal-semiconductor-metal structure have been fabricated on these films. The effects of off-angled sapphire substrates on the surface morphology and crystal quality of β -Ga 2 O 3 films have been systematically investigated. All the results indicate that to some extent the larger off-angled sapphire substrate could lead to the smoother surface morphology and higher crystal quality of β -Ga 2 O 3 films. Reduction in the numbers of in-plane rotational domains for β -Ga 2 O 3 films on off-angled substrates may result in the above-mentioned improvement, which have been confirmed by x-ray diffraction ϕ -scan. β -Ga 2 O 3 film grown on ∼7° off-angled sapphire substrate has ( 400 ) preferred orientation with the single-domain growth mode. Besides, the performance of β -Ga 2 O 3 PDs fabricated on different off-angled substrates show the same trend with changing the off-axis angles. The β -Ga 2 O 3 PD fabricated on ∼7° off-angled sapphire substrate has excellent optical characteristics with large photocurrent to dark current ratio of 430.53 and high UV–visible rejection ratio of 1.42 × 10 3 . These results would be helpful for improving the crystal-quality of hetero-epitaxy β -Ga 2 O 3 films by using off-angled sapphire substrates and fabricating the cost-effective mass-producible solar-blind ultraviolet PDs by sol–gel method.