X-ray microbeam characterisation of crystalline defects in small pixel GaAs:Cr detectors

A newly supplied 80 × 80 chromium compensated GaAs sensor with a matrix of 80 × 80 pixels on a 250 μm pixel pitch has been characterised utilising microbeam mapping techniques at the Diamond Light Source. The GaAs:Cr sensor was mounted to a HEXITEC DAQ system before raster scanning an X-ray beam with area 25 × 25 μm2 in steps of 25 μm, providing sub-pixel resolution spectroscopic imaging. Scans were performed with incident X-ray energies ranging from 12 to 45 keV. Following processing of the data in MatLab 2019b an analysis of defects previously observed in etched GaAs wafers occurred. Findings indicate the presence of regions with reduced charge collection efficiency where up to 88% of incident events show significant charge loss, and changing charge carrier lifetimes across the sensor.