GaAs High Breakdown Voltage Front and Back Side Processed Schottky Detectors for X-ray Detection

Report No. ARL-TR-4308
Authors: Fred Semendy, Satpal Singh, Mark Litz, Priyalal Wijewarnasuriya, Kara Blaine, and Nibir Dhar
Date/Pages: November 2007; 20 pages
Abstract: We have studied the current voltage and X-ray detection using front and back side processed, unintentionally doped bulk gallium-arsenic (GaAs) Schottky detectors and determined that GaAs detectors with a large enough thickness and low enough doping could be used for X-ray imaging, especially for medical applications. In this study, GaAs Schottky detectors were fabricated using front and back side photolithographic processing using Ti/Au for Schottky and Ge/Au/Ni/Au for ohmic contacts. A number of 2¿2 mm detectors were tested. The breakdown voltage reached 600800 V in semi-insulated (SI) GaAs Schottky front and back side processed detectors. For these detectors, the dark current was found to be between 290 nA. These detectors were also characterized with 150 keV, 3mA X-ray radiation and they responded well, showing more than a hundred fold increase in photocurrent due to production of electron hole pairs by the ionization processes. The processing of the detectors and the current-voltage (I-V) and X-ray characterizations are presented in this report.
Distribution: Approved for public release
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Last Update / Reviewed: November 1, 2007