A new GaAs material for X-ray imaging

It is now recognized that X-ray imaging, in particular for medical applications, could be achieved using GaAs detectors provided that it will be possible to grow epitaxial layers at low cost, of large enough thickness (100–300 μm), and low enough doping (1013–1014 cm−3). The aim of this communication is to describe a growth technique, cheap to assemble and run compared to conventional growth techniques, which allows to grow in few hours epitaxial layers of good structural, electrical and optical qualities, with thicknesses ranging from 100 to 500 μm. Doping achieved without taking any precaution concerning contamination is about 1015 cm−3. The electrical characteristics of these layers, as well as the Schottky barriers made on them will be briefly described. We discuss and illustrate with experimental data the means by which the doping can be reduced (by increasing the As antisite concentration through a variation of the growth rate, by decreasing the contamination and by electron irradiation).