Simulation of GaAs 3-D pixel detectors

The performance of an architecture for X-ray pixel detectors is discussed. The three-dimensional (3-D) structure has electrodes which penetrate the bulk of the detector medium allowing low-bias, high-speed operation along with improved charge collection efficiency. We use the modelling package MEDICI to simulate epitaxial gallium arsenide 3-D detectors. This includes an analysis of charge transport and signal formation, with details of the expected charge collection efficiencies. These detectors may be fabricated by a number of means including dry etching. The effect of dry-etch damage on detector performance is analysed as this is potentially an important factor.