Potential of thick GaAs epitaxial layers for pixel detectors

It is now recognised that X-ray imaging, in particular for medical applications, 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 cheap to mount and run compared to conventional techniques, with which epitaxial layers of good structural, electrical, and optical quality, with thickness ranging from 100 to 500 μm can be obtained. Residual doping achieved, without taking any precaution concerning contamination, is in the range 1014–1515 cm−3. The electrical characteristics of these layers, as well as Schottky barriers made on them, are described, discussed, and illustrated with experimental data, a mean by which the doping can be reduced, namely electron irradiation.