Activation properties of Schottky CdTe diodes irradiated by 150 MeV protons

With its high stopping power, Cadmium Telluride (CdTe) has been regarded as a promising semiconductor material for the next generation X/γ-ray detectors, and improved significantly during this decade. In order to apply this device to astrophysics, it is essential to investigate the radiation hardness and background properties induced by cosmic-ray protons. We irradiated Schottky CdTe diodes and a CdTe block with a beam of mono-energetic (150 MeV) protons. The induced radio-activation in CdTe was measured externally with a germanium detector, and internally with the irradiated CdTe diode itself. We successfully identified most of radioactive isotopes induced mainly via (p, xn) reactions, and confirmed that activation background level of the CdTe diode is sufficiently low in orbit. We compared energy resolution and leakage current before and after the irradiation, and also monitored the signals from a calibration source during the irradiation. There have been no significant degradation. CdTe diodes are enough tolerant to radioactivity in orbit.