The effects of proton-induced radiation damage on compound-semiconductor x-ray detectors

Abstract

We report the results of a series of experiments designed to assess the relative radiation hardness of a range of compound semiconductor X-ray detectors. The specific compounds tested were GaAs, InP, CdZnTe, HgI₂ and TlBr, along with an elemental Si device. To allow meaningful comparisons, all devices were of a similar size and, with the exception of the InP detector, had sub-keV energy resolution at 5.9 keV. The irradiations were carried out using the University of Helsinki’s Cyclone 10/5 10 MeV proton cyclotron. Each detector was given six consecutive exposures - the integral fluences being; 2.66 x 10⁹ p cm^-2, 7.98 x 10⁹ p cm^-2, 2.65 x 10¹⁰ p cm^-2, 7.97 x 10¹⁰ p cm^-2, 1.59 x 10¹¹ p cm^-2, and 2.65 x 10¹¹ p cm^-2, respectively. In Si, these correspond to absorbed radiation doses of 2, 6, 20, 60, 120 and 200 krads. During the exposures, the detectors were kept unbiased and at room temperature. After each irradiation, the effects of the exposure were assessed, both at room temperature and at a reduced temperature using ⁵⁵Fe, ¹⁰⁹Cd and ²⁴¹Am radioactive sources. It was found that with the exception of the HgI₂ and TlBr detectors all materials showed varying degrees of damage effects.