From charge tracking to signal formation: A multi-body approach for simulating Coulomb effects in semiconductor detectors

We present a simulation code for the solution of the electron–hole dynamics and signal formation in 3D semiconductor radiation detectors. The code adopts a multi-body approach, i.e. the evolution and interaction of the charge cloud is tracked on an individual carrier basis, using a combination of numerical ODE solvers and Monte Carlo methods. Particular emphasis is devoted to the treatment of the Coulomb interaction, critical for the correct simulation of high-density ionization tracks. This multi-body approach sheds light on the phenomenology of the plasma effect, revealing the underlying co-dependence between local field screening and carrier binding. In addition, a dynamic time-step algorithm allows for accurate tracking at virtually any time scale within accessible computational times. By nature, the problem makes the code architecture ideal for GPU-based parallel computing. The method is validated through comparison with experimental data from a p+nn+ silicon diode under different bias and charge injection conditions representative of realistic scenarios encountered in modern X-ray facilities e.g. FELs.