Optimization of GaN/InGaN Heterojunction Phototransistor

A numerical model of GaN/In0.03Ga0.97N/GaN heterojunction phototransistor (HPT) with a floating base is built by TCAD. The simulated dark and light current characteristics are in good agreement with the experimental results. The performance of the device under both low and high voltages is studied, and the effects of carrier concentration and different materials are discussed in detail. It is found that the higher carrier concentration of collector or with the collector material of GaN can form higher electric field in base-to-collector junction, which will result in higher current gain and lower avalanche breakdown voltage. What is more, the HPT with the lower doped and graded layer between base and collector will obtain better device performance under low voltages.