InGaP/GaAs heterojunction phototransistors for ultra-low optical power detection

Optoelectronic conversion gain of floating base InGaP/GaAs heterojunction bipolar phototransistors (HPTs) with and without base contact metal was investigated. The fabricated HPTs without base contact metal showed the higher optical gain compared to those with base contact metal. The devices exhibited very high optical gain of 162 at optical power of 1.74 muW under the 640 nm illumination.