Characterization of chromium compensated GaAs as an X-ray sensor material for charge-integrating pixel array detectors

Abstract

We studied the properties of chromium compensated GaAs when coupled to charge\nintegrating ASICs as a function of detector temperature, applied bias and x-ray\ntube energy. The material is a photoresistor and can be biased to collect\neither electrons or holes by the pixel circuitry. Both are studied here.\nPrevious studies have shown substantial hole trapping. This trapping and other\nsensor properties give rise to several non-ideal effects which include an\nextended point spread function, variations in the effective pixel size, and\nrate dependent offset shifts. The magnitude of these effects varies with\ntemperature and bias, mandating good temperature uniformity in the sensor and\nvery good temperature stabilization, as well as a carefully selected bias\nvoltage.\n