Optical characteristics of InGaP/GaAs HPTs

In this paper, we examined the optical characteristics of InGaP/GaAs hetero junction phototransistor (HPT) directly compared with AlGaAs/GaAs HPT for t he first time. Because of its inherent good electrical properties, InGaP/Ga As HPT produced the high optical gain of about 61 at V-C = 3 V, I-B = 2 muA , for the input optical power of 1.23 muW This is 2.5 times as high as that of AlGaAs/GaAs HPT. In the transient response, InGaP/GaAs HPT was a little inferior to AlGaAs/GaAs HPT. This is due to the longer time delay caused b y the photo-generated hole accumulation at the interface of heterojunction. The extended response time can be overcome by using the small load resista nce in conjunction with the advantage of the superior optical gain.