Fabrication and characterization of GaN ultraviolet photodetector prepared by growing on geometrical patterned sapphire substrate

GaN metal-semiconductor-metal ultraviolet (UV) photodetector is grown on geometrical patterned sapphire substrate using metalorganic chemical vapor deposition. Under 5-V reverse bias, the photodetector grown on geometrical patterned sapphire substrate exhibits a lower dark current, a higher photocurrent, a better maximum responsivity, and a larger UV-to-visible rejection ratio as compare with those of the photodetector grown on conventional flat sapphire substrate. These improved properties may all be attributed to the reduction of threading dislocation density and the internal reflection and/or scattering effect on the geometrical pattern of the substrate.