Modeling of processes of charge division and collection in GaAs detectors taking into account trapping effects

A mathematical modeling of processes of charge division and collection in GaAs detectors has been carried out. The charge carriers behavior has been described by the system of continuity equations and Poissonʹs equation. We studied a case when semi-insulating (SI) GaAs contains deep centers of only one type with the abrupt cross-section dependence on field. A concentration of empty traps was taken at a level of 1015–1016 cm−3. All the parameters of deep centers correspond to the EL2 center which is dominant in SI GaAs. Interaction with γ-rays and electrons were simulated by electron–hole packets of corresponding dimensions. It was shown that dynamics of charge division in the case of trapping and without trapping is determined by three factors: (1) the electric field strength value in the region of electron–hole pairs creation; (2) a concentration of non-equilibrium charge carriers in that region (i.e. the ionizing radiation type); (3) the region dimensions.