Quasi-direct UV/blue GaP avalanche photodetectors

GaP avalanche photodiodes, with thin device layers have been processed, utilizing both p-i-n and recessed window p-i-n structures, as well as a Schottky structure. The results showed low dark currents, good quantum efficiency (QE), and high gains up to 10(3), with good uniformity across the wafer. The peak QE at 440 nm indicated F-valley absorption, rather than band-edge absorption. The recess window photodiodes exhibited enhanced UV detection as a result of reduced absorption and recombination in the undepleted p-layer. Additionally, the Schottky structure demonstrated potential for further enhanced UV detection, by employing a thin semitransparent contact.