Voltage-source controlled double-emitter phototransistors grown by low-pressure MOCVD

Single- and double-emitter heterojunction phototransistors with the same total emitter area have been fabricated and qualitatively investigated. The double emitters in two kinds of DE-HPTs are designed to have area ratio of 1:1 and 1:2, respectively. Both a positive and a negative voltage applied to the second emitter can control and enhance the collector photocurrent. It is found that 1:2 and 1:1 DE-HPTs exhibit 1.85- and 1.5-fold optical gain of that from a SE-HPT, respectively.