Implications of carrier mobility limitations for GaAs as an x-ray detector

Theoretically, gallium arsenide detectors offer an attractive alternative to silicon for the high energy x- ray astronomer, due to the greater absorption power of the material. However, in practice, GaAs detectors made from bulk-grown crystals have a spectral resolution which falls well short of both expectation and that achieved by silicon detectors of comparable thickness. In contrast, a detector fabricated from GaAs grown by the liquid phase epitaxial (LPE) process displays full charge collection with a resolution in agreement with that expected from measurements of leakage current and device capacitance. Experimental results are presented showing the level of spectral resolution possible in a variety of GaAs detectors, including Liquid Enhancement Czochralski material from various manufacturers, Vertical Bridgeman and LPE material. Both the detector performance and the electrical characteristics (voltage-current, noise, etc) have been explored for each device.