X-ray detectors based on semi-insulating GaAs substrate.

Semi-insulating GaAs is suitable as detector for X-rays and particles. Compared to silicon, charge carriers in GaAs have less effective mass, so they gain a higher acceleration. The detectors operate as Schottky diodes. Design and processing were carried out at the IAF in Freiburg. The layout contains quadratic diodes of various sizes (2x2 square millimetre, 3x3 square millimetre, etc.) and also microstrip detectors. Test measurements were made with Alpha-, Beta- and Gamma-rays. For the first time X-rays down to 20 keV have been observed with room temperature GaAs. With Gamma-radiation of high57Co, 122 keV, an energy resolution of 18 % FWHM was obtained. It is planned to integrate signal processing fast electronics on the same wafer. Also discussed is a data transfer by optoelectronical means, as for example laser diodes and MSM photodiodes.