TCAD simulations of internal amplification in high purity germanium detectors

Simulations of internal amplification processes in high purity germanium (HPGe) detectors for gamma radiation are presented. The Synopsys Sentaurus Technology Computer-Aided Design (TCAD) package was employed to study conditions favourable to charge multiplication within volume of the detector. The physics model was developed, and validated where possible against known results from existing literature. The model was then applied to a new detector and a systematic study of the measurable parameters influencing charge collection and electric field profile was performed. Evidence of the internal amplification in the developed HPGe detector model was demonstrated at 4 kV bias voltage with anode diameter below 100 μm, corresponding to 16 kV/cm electric field and when an additional dopant with concentrations >5×10¹⁰cm^-3 under the anode implanted. These effects were also simulated and observed in silicon detectors, giving additional confidence in the validity of the findings for germanium, presented in this work.