Development of an electron track-structure mode for arbitrary semiconductor materials in PHITS

Hirata, Yuho   ; Kai, Takeshi   ; Ogawa, Tatsuhiko   ; Matsuya, Yusuke*  ; Sato, Tatsuhiko   

Optimization of semiconductor detector design requires theoretical analysis of the process of radiation conversion to carriers (excited electrons) in semiconductor materials. We, therefore, developed an electron track-structure code that can trace an incident electron trajectory down to a few eV and simulate many excited electron productions in semiconductors, named ETSART, and implemented it into PHITS. The accuracy of ETSART was validated by comparing calculated electron ranges in semiconductor materials with the corresponding data recommended in ICRU Report 37 and obtained from another simulation code. The average energy required to produce a single excited electron (epsilon value) is an important value that describes the characteristics of semiconductor detectors. Using ETSART, we computed the epsilon values in various semiconductors and found that the calculated epsilon values cannot be fitted well with a linear model of the band-gap energy. ETSART is expected to be useful for initial and mechanistic evaluations of electron-hole generation in undiscovered materials.