A comparison between GaAs and CdTe for X-ray imaging

We have grown 4 inch GaAs epitaxial layers of thickness ranging from 100 to 600 /spl mu/m. With such layers we made pixel X-ray detectors where each pixel is a p/sup +//i/n/sup +/ mesa structure in which the grown layer is the i region. The aim of this communication is to describe, prior to the evaluation of an image, the performances of such a detector in terms of homogeneity, reverse dark current, linearity, response time, dynamic range and charge collection efficiency. We shall also describe how the current induced by 100 kV X-rays in a detector made of a 115-/spl mu/m thick GaAs layer compares with that produced in the same conditions by a 1-mm thick CdTe detector.