New model for a GaAs x-ray pixel detector

The performance of a GaAs semiconductor matrix pixel detector, designed for intrinsic digital radiography, is evaluated. Electrical characterisation of different pixels is realised and a new numerical model is indicated for the charge and the current due to electron hole pairs generated by the ionising radiation. The model, taking into account trapping and generated carrier phenomena, allows the indirect evaluation of the charge collection efficiency through a preliminary determination of the real trap distribution and transport parameters depending on the electric field. The numerical simulations obtained, confirming the electrical behaviour, make a more accurate design of the electronic front-end possible.