The InP based HBT(heterojunction bipolar transistor used for OEIC(optoelectronic integrated circuits)is analysed,and a novel collector layer structure is proposed,which is achieved by introducing p-InGaAs layer and N-InP layer with specific thickness and doping level between the collector and subcollector of SHBT(single heterojunction bipolar transistor).This composite collector structure is suitable for integrated pin photodetector and solves the poor breakdown voltage of SHBT and the electron blocking efforts of traditional DHBT(double heterojunction bipolar transistor).In addition,the epitaxy layer of this structure is easy to grow and the electron velocity of collector is high.