GaAs X-ray detector characterization through a 3D finite element model

In this paper the characterization of a GaAs X-ray pixel detector is presented. The performance is obtained experimentally by a detector using a Schottky diode on a semi-insulating, Vertical Gradient Freeze, (100) oriented single crystal GaAs substrate. Moreover, a new 3D Model based on the Finite Element Method is shown which takes into account the carrier trapping and emission phenomena. The model analyzes the single event upset for a photon hitting the pixel surface in any direction. The main advantage of the model used is its ability to determine the influence of both the position of the impact point and of the slope of the particle trajectory with respect to the pixel surface on the detector performance. The numerical simulations obtained confirm the experimental values and permit 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.