  InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in
practical applications requiring near-infrared photon counting such as quantum
key distribution (QKD). Photon detection efficiency and dark count rate are the
intrinsic parameters of InGaAs/InP SPADs, due to the fact that their
performances cannot be improved using different quenching electronics given the
same operation conditions. After modeling these parameters and developing a
simulation platform for InGaAs/InP SPADs, we investigate the semiconductor
structure design and optimization. The parameters of photon detection
efficiency and dark count rate highly depend on the variables of absorption
layer thickness, multiplication layer thickness, excess bias voltage and
temperature. By evaluating the decoy-state QKD performance, the variables for
SPAD design and operation can be globally optimized. Such optimization from the
perspective of specific applications can provide an effective approach to
design high-performance InGaAs/InP SPADs.
