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.