A new GaAs material for X-ray imaging

It is now recognized that X-ray imaging, in particular for medical applicat ions, could be achieved using GaAs detectors provided that it will be possi ble to grow epitaxial layers at low cost, of large enough thickness (100-30 0 mum), and low enough doping (10(13)-10(14) cm(-3)). The aim of this commu nication is to describe a growth technique, cheap to assemble and run compa red to conventional growth techniques, which allows to grow in few hours ep itaxial layers of good structural, electrical and optical qualities, with t hicknesses ranging from 100 to 500 mum. Doping achieved without taking any precaution concerning contamination is about 10(15) cm(-3). The electrical characteristics of these layers, as well as the Schottky barriers made on t hem will be briefly described. We discuss and illustrate with experimental data the means by which the doping can be reduced (by increasing the As ant isite concentration through a variation of the growth rate, by decreasing t he contamination and by electron irradiation). (C) 2001 Elsevier Science B. V. All rights reserved.