InGaAsP/InP phototransistor-based detectors

Two kinds of phototransistors-a Schottky Collector Phototransistor (SCPT) and a Photo-Darlington Transistor (PDT), which should prove useful for switching and high current application, respectively-have been fabricated from InGaAsP/InP wafers grown by LPE. The SCPT exhibited gain greater than 100. The characteristics of the SCPT are compared with those of n-p-n phototransistors and are found to differ considerably. A PDT with a gain of 100 has been fabricated, and collector currents over 100 mA can be maintained without paying special attention to the heat sink. The details of the fabrication procedures and characteristics of these devices are described in this paper.