Single Photon Avalanche Diode with Monte Carlo Simulations: PDE, Jitter and Quench Probability

Single Photon Avalanche Diodes (SPAD) are key optoelectronic detectors for medical imaging, camera ranging and automotive laser imaging detection and ranging (LiDAR) applications. Today, most of SPADs in the Time Of Flight (TOF) market are composed of a micrometric Silicon PN junction associated to a proximity CMOS electronics biasing the system above the breakdown voltage. These devices present low noise, high pixel-matrix integration capabilities, but their Photon Detection Efficiency (PDE) is relatively modest in the near infrared operating region (achieving typically only few percent at a wavelength of 940 nm). A considerable optimisation of the SPAD design is currently on going at an industrial level with a view of increasing the PDE without compromising the timing statistic response to avalanche (Jitter) and its quench probability. Within these perspectives, standard commercial Technology-Computer-Assisted-Design (TCAD) simulations can only provide a limited guidance for technological and design splits optimisation since they are based on deterministic solvers that are unable to capture these stochastic figures of merit. Since the seminal work from Spinelli [1] clearly showing that Monte Carlo simulations predictions can compare favourably with experimental measurements of PDE and timing resolution, the Monte Carlo method can be considered to be a useful one for the design of improved structures. It has been recently applied to optimize the PDE and Jitter of Silicon [3] and InGaAs SPADs [4],[5]. In this abstract we report a rigorous comparison between Monte Carlo predictions and measurements of PDE and Jitter. We also discuss in detail, the quench probability of these diodes once in avalanche. This latter point has rarely been discussed in literature and to the best of our knowledge never addressed within a Monte Carlo perspective.