Al x Ga 1−x N:Si Schottky barrier photodiodes with fast response and high detectivity

Abstract

Gold and nickel Schottky barrier photovoltaic detectors have been fabricated on Si-doped AlxGa1−xN layers (0⩽x⩽0.22) grown on sapphire by metalorganic vapor phase epitaxy. Responsivity is independent of the Schottky metal or diode size, and also of the incident power in the range measured (10 mW/m2–2 kW/m2). A higher visible rejection has been observed in the spectral response of Au photodiodes (>103). Time response is resistance-capacitance limited, with time constants as short as 14 ns in Al0.22Ga0.78N diodes. Low frequency noise studies are also presented, and detectivities of 6.1×107 and 1.2×107 mHz1/2 W−1 are determined in GaN/Au and Al0.22Ga0.78N/Au detectors, at −2 V bias.