The effects of nonphysical carrier velocities in high-gradient single event track simulations

This paper deals with two modeling issues imposed by low-energy ion track structures. In most PISCES-like semiconductor charge transport simulation codes, the diffusion velocity, as predicted by Fick's Law, exceeds thermal velocity at high-gradient regions of the low-energy ion initial track structure. Our numerical study results indicate this nonphysical diffusion velocity effect does not affect the fidelity of the track temporal evolution; thus, it plays no part in a macroscopic charge collection device level simulation. In addition, the analysis on the temporal evolution of the narrow track structures provides an efficient gridding scheme to eliminate the need of computationally expensive tight mesh to describe the initial narrow tracks of low-energy ions.