Schottky rectifiers fabricated on free-standing GaN substrates

Abstract

GaN Schottky rectifiers have been fabricated on free-standing substrates and on epi/substrate structures. Forward turn-on voltages were as low as 3 V at 25°C. Reverse recovery was complete in <600 ns, with a characteristic time constant of ∼163 ns. The temperature coefficient for reverse breakdown voltage ( V B) was −2.5±0.6 V K −1 which is much lower than for lateral rectifiers reported previously, where values up to −30 V K −1 were achieved. Reverse currents increased with rectifying contact diameter and V B decreased with increasing contact size. The best on-state resistance was 20.5 m Ω cm −2 for diodes with V B=450 V, producing a figure-of-merit ( V B) 2/ R ON of ∼10 MW cm −2.