Comparison of Tuning Performance Characteristics of Dual-Emitter Phototransistor with Biased Emitter and Heterojunction Phototransistor with Biased Base

摘要

An InGaP/GaAs dual-emitter heterojunction phototransistor (DEPT) with a voltage-biased emitter is compared with a conventional heterojunction phototransistor (HPT) with a voltage-biased base. 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 power- and voltage-tunable optical gains are obtained in the DEPT, while only the voltage-tunable optical gain in the HPT. In addition, the maximum optical gain (32.3) obtained in the DEPT is 20-fold that (1.64) in the HPT. Experimental results show that 1) the voltage-tunable optical gain ranges from 0.8 to 1.64 with a gain-tuning efficiency of only 4.4 V~(-1) for the HPT and that 2) the DEPT exhibits a voltage-tunable optical gain ranging from 12.9 to 32.3 with a maximum gain-tuning efficiency of 43.4 V~(-1). Furthermore, a simple circuit model is developed to describe well the optical performance tuned by a voltage for both the DEPT and HPT. Experimental and modelling results indicate that the DEPT is very promising for optoelectronic applications when a low optical power is used.