Breakdown mechanisms in Al(GaN) MSM photodetectors

摘要

AlGaN based interdigital metal-semiconductor-metal (MSM) photodetectors with 14 percent Al have been successfully grown and fabricate don sapphire substrates. The devices exhibit large gains up to 10$+6$/ at high bias voltages, but with very high dark currents, $GRT 1 mA and very long detector responses, $GRT 60 seconds. A negative temperature coefficient for the breakdown voltage was observed indicating that tunneling is occurring. However, at high bias voltages, avalanche breakdown also appears to be present since a constant breakdown field of 10$+5$/ V/cm was obtained independent of MSM geometry. Avalanche breakdown is nucleated at the non-uniform field distribution at the edge of the MSM finger.