Modeling, Simulation Methods and Characterization of Photon Detection Probability in CMOS-SPAD

Area of Science:

• Photonics and Semiconductor Devices
• Space Systems Engineering
• Computational Modeling

Background:

• Single-Photon Avalanche Diodes (SPAD) in CMOS technology are crucial for future space-borne Light Detection and Ranging (Lidar) systems.
• Photon Detection Probability (PDP) is a key SPAD performance metric, directly impacting Lidar sensitivity and system design parameters like laser power and telescope diameter.

Purpose of the Study:

• To develop and validate a predictive model for the Photon Detection Probability (PDP) of CMOS SPADs.
• To enhance the accuracy of PDP simulations by integrating process doping profiles, TCAD simulations, and custom routines.

Main Methods:

• Acquired CMOS process doping profiles through measurements.
• Utilized Technology Computer-Aided Design (TCAD) simulations to model SPAD behavior.
• Developed a Matlab routine to integrate simulation data and predict PDP.
• Compared simulation results with experimental data from a fabricated CMOS 180 nm SPAD.

Main Results:

• Achieved good agreement between predicted and measured PDP values, with a mean error of approximately 18.5% across wavelengths from 450 to 950 nm.
• Validated the model for excess voltages ranging from 15% to 30% of the breakdown voltage.
• Determined that simulating PDP without substrate contribution introduces a moderate precision loss of about 4.5 percentage points.

Conclusions:

• The developed model accurately predicts CMOS SPAD PDP, crucial for optimizing Lidar space systems.
• The simulation methodology provides a valuable tool for designing and evaluating SPADs for demanding space applications.
• Understanding substrate contribution is important, but simulations can be simplified with acceptable precision loss.