Effects or Proton-Induced Radiation Damage on Cadmium Zinc Telluride Pixel Detectors

Abstract

Cadmium zinc telluride (CdZnTe) is a room temperature solid state material with many properties attractive to space- borne astrophysical instrumentation. Irradiation of monolithic CdZnTe detectors with 199 MeV protons shows that proton-induced radiation damage causes an increase in electron trapping in the material. Small-pixel and strip CdZnTe detectors which rely on efficient electron collection are particularly sensitive to changes in the electron mean free path, which can result in significant changes in the spectral response. Using a charge transport model, we calculate the effects of the observed radiation damage on spectral response for pixel detectors of several geometries. A degradation in spectral response is observed which is most pronounced for small-pixel detectors. The magnitude of the effects indicate that depending on pixel size and the desire for good spectral performance annealing may be necessary to maintain good detector performance after approximately 1 - 2 years in low-earth orbit.