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/sup 3/, with good uniformity across the wafer. The peak QE at 440 nm indicated /spl Gamma/-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.