Potential of thick GaAs epitaxial layers for pixel detectors

It is now recognised that X-ray imaging, in particular for medical applicat ions, could be achieved using GaAs detectors provided that epitaxial layers of large enough thickness, and low enough doping can be grown at low cost. The aim of this communication is to describe a growth technique, that is c heap to mount and run compared to conventional techniques, with which epita xial layers of good structural, electrical, and optical quality, with thick ness ranging from 100 to 500 mum can be obtained. Residual doping achieved, without taking any precaution concerning contamination, is in the range 10 (14)-15(15) cm(-3). Th, electrical characteristics of these layers, as well as Schottky barriers made on them, are described, discussed, and illustrat ed with experimental data, a mean by which the doping can be reduced, namel y electron irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.