Design Criteria for InGaAs/InP Single-Photon Avalanche Diode

We provide a detailed insight on the design of InGaAs/InP single-photon avalanche diode (SPAD) for 1.55- μm photon detection. In order to lower SPAD noise [the dark count rate (DCR)] without lowering photon detection efficiency (PDE) or increasing afterpulsing, it is important to optimize detector vertical layer structure and diffusion profiles. We present simulations of SPAD structures with different models, including custom ones. We discuss the influences of multiplication region thickness and doping, absorption region thickness, and electric-field distribution on SPAD performance. Multiplication region thickness strongly affects tunneling generation, whereas a thicker absorption region gives higher absorption efficiency but reduces trigger efficiency. Their optimal values depend on InP and InGaAs material quality and on device operating conditions. We show how electric field within InGaAs must be chosen as a tradeoff between heterobarrier transit efficiency and carrier generation.