Charge Persistence in InGaAs/InP Single-Photon Avalanche Diodes

We present a detailed characterization and modeling of the charge persistence effect that impacts InGaAs/InP single-photon avalanche diodes. Such phenomenon is due to holes that pile-up at the heterointerface outside the active area and has two main consequences: 1) higher noise (equivalent to higher dark count rate), not decreasing as expected at low temperature and 2) possible distortion of the acquired time-resolved waveforms (due to such signal-correlated noise). We propose a model that describes: 1) the generation of holes at the detector periphery in the InGaAs layer; 2) their accumulation at the heterointerface; 3) their subsequent diffusion toward the active area within the InGaAs layer; and 4) their resulting drift to the high field depleted InP region, where the unwelcome spurious avalanche is eventually triggered. We support our model by detailed experimental measurements and simulations. Finally, we propose simple approaches for designing detectors less sensitive to this type of noise.