Design and Characterization of 1×128 In0.53Ga0.47As/InP Photodetector Linear Array with Improved Optical Sensitivity and Shunt Resistance

An InGaAs/InP heterojunction phototransistor (HPT) 1×128 one dimensional array chip with an improved optical sensitivity and shunt resistance has been designed and characterized for the detection of a low light signal intensity. We also present epitaxial structures and an equivalent model for optimizing the optical gain and shunt resistance characteristics. The device operation mechanism and experimental results are discussed. The experimental results show that our device has an optical sensitivity of 46 A/W, which is significantly higher than that of a conventional PIN photodetector with the same light absorbing area. This high sensitivity originates from the optical gain-enhanced device structure. The typical optical gain is approximately 94, indicating that HPTs are 94 times more sensitive than PIN photodetectors. The proposed HPT also has over 100–200 of kΩ shunt resistance and a high optical sensitivity under a low illumination condition, which is sufficient for effective signal conversion through a trans-impedance amplifier circuit. In addition, we also discuss a high-power optical-stress-induced dark current reduction effect that is similar to a thermal-annealing-induced dark current reduction effect. of An optical-stress-induced dark current reduction of approximately 1 order is observed in our experiments.