TCAD Simulation of Avalanche Breakdown Voltage in GM-APDs

In this paper, the breakdown voltage (VBD) temperature behavior in Geiger-Mode avalanche photodiodes (GM-APDs) is investigated by means of both experimental characterization of silicon photomultiplier (SiPMs) fabricated at FBK-IRST and one-dimensional TCAD simulations of GM-APDs. The analysis aims at relating both the VBD and its temperature coefficient to relevant technological device parameters, such as epitaxial layer thickness and doping concentration, in the context of device performance optimization for PET (positron emission tomography) applications. We show that the properties of the epitaxial layer regulate the extension of the depleted region and play therefore a crucial role in determining the device breakdown voltage and its temperature coefficient. We also show that only by recurring to an energy-balance transport model, the TCAD simulations are able to capture the dependences of VBD on the device structural characteristics and on temperature that are experimentally observed. We finally report on TCAD simulations of VBD variability in correlation to possible fluctuations in the epitaxial layer properties