EFFECTS OF MATERIAL IMPROVEMENT ON CZT DETECTORS

CZT material quality improvement has been achieved by optimizing the crystal growth process. N-type conductivity has been measured on as-grown, undoped, Cd0.9Zn0.1Te. Cd0.85Zn0.15Te crystals have been grown. for producing high resistivity CZT radiation detectors. The best FWHM of 57Co 122KeV spectrum was measured to be 3.7% and (μτ)e was 3 x 10-3 cm2V-1. The microscopic gamma ray response using a beam size of 10 (micro)m has been used to map the entire 4 mm x 4 mm detector. Several black spots indicating no signal responses were observed while all other areas showed an average of 65-70% collection efficiency. The black spots suggest that at those locations, the Te precipitates are larger than 10 (micro)m. Detailed microscopic infrared transmission measurement on the sample found that most Te precipitates have sizes of 4-6 (micro)m. Theoretical analysis of the results suggests that singly and doubly ionized TeCdVCd2 might be the shallow and deep donors previously assigned to TeCd by us