Comparison of Optical Characteristics of Three-Terminal Dual-Emitter Phototransistor and Three-Terminal Heterojunction Phototransislor

摘要

Dual-emitter heterojunction phototransistors (DEPT) with an voltage-biased emitter is compared with the conventional heterojunction phototransistor with a voltage-biased emitter. There are four (three) operating regions in the photocurrent-voltage characteristics of the DEPT (HPT): negative-saturation, negative-tuning, positive-tuning, and positive-saturation (cutoff, positive-tuning, and positive-saturation) regions. The obtained optical gains are only 0.784～l .64 with a gain-tuning efficiency of 4.4 V~(-1) for the HPT while those are in the range of 12.9 ～ 32.3 with the maximum gain-tuning efficiency of 43.4 V~(-1) for the DEPT. The power- and voltage-tunable optical gains are both expected for the DEPT. However, the conventional HPT exhibits only voltage-tunable characteristics. DEPTs with different emitter area ratio are also discussed. The maximum gain-tuning efficiency is 75.3 for the DEPT with emitter area ratio of 8:1 under optical power of 0.423 μW. The obtained results introduce the potential of employing the DEPT for low-power optical detection.