Performances of epitaxial GaAs p/i/n structures for X-ray imaging

We have realized 150 μm×150 μm pixels using ion implantation followed by photolithography, metallic contact evaporation and chemical etching on about 200 μm thick GaAs epitaxial layers. These layers were grown on n+ and p+ substrates by an already described Chemical Reaction technique, which is economical, non-polluting and can attain growth rates of several microns per minute. The mesa p+/i/n+ pixel were characterized using current–voltage and capacitance–voltage measurements. The charge collection efficiency was evaluated by photoconductivity measurements under typical conditions of standard radiological examinations.