Characterization of high-resistivity CdTe crystals for γ-ray detectors

High-resistivity CdTe crystals were grown from Te-rich solution doped with Cl by the temperature gradient solution growth (TGSG) method. The room-temperature resistivity of the undoped crystals was about 103 Ω cm, and rose abruptly to > 109 Ω cm for a doping concentration of Cl ranging from 500 to 5000 ppm. The mobility—lifetime (μτ) product for both electrons and holes decreased with increasing Cl concentration. The best μτ values of 7.22 × 10−4 cm2 V−1 for electrons and 6.24 × 10−5 cm2 V−1 for holes were obtained at a Cl concentration of 500 ppm. The quality of the crystals was characterized by means of Fourier-transform infrared spectroscopy, photoluminescence analysis and γ-ray detection test. γ-ray detectors with a size of 3 × 3 × 1 mm3, fabricated from high resistivity TGSG crystals, showed energy resolutions (FWHM) of 6.9 keV for 122 keV γ-rays from 57Co and 22.4 keV for 662 keV γ-rays from 137Cs.