An Analog CMOS Silicon Photomultiplier Using Perimeter-Gated Single-Photon Avalanche Diodes

Perimeter-gated single-photon avalanche diodes (PGSPADs) have been shown to mitigate premature edge breakdown without unduly increasing the area of the device. PGSPADs are three terminal devices. In this paper, we develop a probability-based SPICE model for the PGSPAD and fully characterize an $18 \times 18$ pixel analog PGSPAD-based CMOS silicon photomultiplier (SiPM). The noise model is derived using theories of carrier thermal generation, carrier diffusion, and inter-band tunneling. Parameters are derived using fabricated PGSPAD devices and model validity is verified with experimental measurements. The designed PGSPAD SiPM is implemented in standard $0.5~\mu \text{m}$ 2-poly, 3-metal CMOS process, and is characterized for dark current, sensitivity, and signal-to-noise ratio (SNR) throughout the visible spectral range for varying bias voltages. Models show that the reduction of dark events in the PGPSAD is primarily caused by a reduction in band-to-band tunneling. Thus, as a function of the applied gate voltage the PGPSAD shows an improvement of SNR over a range of 1 to 1150. The sensitivity of the presented SiPM is $1.06 \times 10^{3}$ A/W/cm2. The designed PGSPAD SiPM shows great promise over standard SiPM for applications, such as neutron detection which requires high sensitivities and high SNRs.