The chip of the four-quadrant InGaAs APD in this paper is designed in a frontal incident planar structure and its material part is an SAGM APD.On the basis of systematical analysis and calculation of its important parameters

such as response time

dark current and responsivity

the optimized structural and the technological parameters are given.The test results show that its response time is ≤1.5 ns

responsivity ≥9.5 A/W and dark current ≤40 nA.As the PN junction and multiplication layer are set under the surface of the device in the reliability design

the surface leakage current can be effectively restrained and the reliability of the device improved.