Thesis on SPAD Quenching

University of Paris-Saclay publishes o PhD thesis "Modeling and simulation of the electrical behavior and the quenching efficiency of Single-Photon Avalanche Diodes" by Yassine Oussaiti.

"Single-photon avalanche diodes (SPADs) emerged as the most convenient photodetectors for many photon-counting applications, taking advantage of their high detection efficiencies and fast timing responses. Over the past years, their design rules have been evolving to reach more aggressive performances. Usually, trade-offs are required to meet the different constraints.To face these technological challenges, the development of reliable models to describe the device operation and predict the relevant figures-of-merit is compulsory. Evidently, the numerical solvers must be both physics-based and computationally efficient.This Ph.D. work aims to improve the modeling of silicon SPADs, focusing on the avalanche build-up and the quenching efficiency. After a state-of-the-art overview, we investigate various device architectures and potential technological improvements using TCAD methods. We highlight the role of calibrated models and scalability laws in predicting the electrical response.Furthermore, we present a Verilog-A model accounting for the temporal current build-up in SPADs. The important parameters of this model are fitted on TCAD mixed-mode predictions. Importantly, the resulting SPICE simulations of the quenching compare favorably with measurements, allowing a pixel designer to optimize circuits.Since standard TCAD tools are based on deterministic models, the stochastic description of carriers is limited. Hence, Monte Carlo algorithms are used to simulate the statistical behavior of these photodiodes, with a particular attention on the photon detection efficiency and timing jitter. The good agreement between simulation results and experiments confirms the method's accuracy, and demonstrates its ability to assist the development of new generation SPADs."