Microscopic modelling of semi-insulating GaAs detectors

We present a drift-diffusion model of semi-insulating n-GaAs detectors, taking into account the presence of hot-carrier dynamics, conduction band features and the kinetics of trapping and detrapping from deep and shallow centres. We provide unambiguous evidence of a field-enhanced capture cross section for EL2 and EL3 centres as conjectured by McGregor [1] for the case of EL2. This result is shown to be strictly correlated with the active thickness of the detector varying almost linearly with the applied voltage, in excellent agreement with recent experimental measurements performed with the Optical Beam-Induced Currents (OBIC) technique. Evidence of Poole-Frenkel effects at the highest applied voltages is provided by the current-voltage characteristics.