Novel high-gain and high-speed SnO2/AlGaN ultraviolet heterojunction phototransistor

Abstract A SnO 2 /AlGaN ultraviolet heterojunction phototransistor, which achieves high gain and fast speed based on longitudinal and lateral confinement of photogenerated holes, was proposed and developed in this work. The orthogonal transport mechanism of holes enhanced the localization effect of photogenerated holes at the base and meanwhile reduced the recombination of holes and electrons there, which thereby lowered the base barrier and promoted electron transport, resulting in high gain and fast response. The fabricated devices showed a small dark current of lower than 10 pA below 20 V bias, an ultra-high gain of 2.2×10 5 under 315 nm illumination, a very large photo-to-dark current ratio of 1.5×10 8 at 20 V, and a prompt impulse response with a rise /fall time of 1.2 μs/91.1 μs.