MICROSCOPIC MODELING OF SEMIINSULATING 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 a nd shallow centres. We provide unambiguous evidence of a field-enhance d capture cross section for EL2 and EL3 centres as conjectured by McGr egor [1] for the case of EL2. This result is shown to be strictly corr elated with the active thickness of the detector varying almost linear ly with the applied voltage, in excellent agreement with recent experi mental measurements performed with the Optical Beam-Induced Currents ( OBIC) technique. Evidence of Poole-Frenkel effects at the highest appl ied voltages is provided by the current-voltage characteristics.