Tuneable Breakdown Voltage in Amorphous Silicon P-I-N Photo-detectors for Single Photon Imaging

Single Photon Avalanche Diodes (SPAD) have been widely used as the photo-detectors of choice in CMOS single photon imagers. These are p-n diodes which are biased at a voltage higher than its breakdown voltage and hence, suffer from high power requirements. Additionally, the breakdown voltage of such diodes is predetermined by the fabrication process and cannot be tuned easily. Reducing the breakdown voltage in such diodes can result in reduced power consumption, consequently, enabling the design of low power imagers. In this paper, we present a novel hydrogenated amorphous silicon (a-Si:H) p-i-n diode operating in avalanche mode for single photon imaging applications. Built with nanometer dimensions, simulation results demonstrate that breakdown voltage tunability of these diodes can be achieved by varying the thin film layer thickness and doping concentration of each layer, leading to breakdown voltage as low as 6 V.