Temperature Dependence of Avalanche Breakdown in Silicon Detectors

Avalanche breakdown has been measured in silicon detectors using low-gain avalanche diodes (LGADs) produced by CNM and HPK, at temperatures between 25 and 325 K. The measured avalanche breakdown has been compared with the prediction of different impact ionization models proposed in the literature, with strong disagreements found. This work proposes a new analytical impact ionization expression to get a more accurate model of the avalanche breakdown in silicon-based devices. Using a local analysis, new effective ionization coefficients are proposed that better cover the range in temperatures and the electric field studied in this work. A simplified avalanche breakdown condition, which depends on the device characteristics and operational temperature, is derived as a function of the impact ionization coefficients.