Characterization of Cd0.9Zn0.1Te schottky diodes for high resolution nuclear radiation detectors

High barrier cadmium zinc telluride (CZT) Schottky diodes with very low reverse leakage current have been fabricated and characterized for high resolution gamma ray detectors. The diodes were made using Cd_0.9Zn_0.1Te detector grade crystals grown from zone refined Cd, Zn, and Te (7N) precursor materials using low temperature tellurium solvent method. Various crystallographic defects due to Te-inclusions/precipitates were identified and characterized using electron beam induced current (EBIC) measurement technique for the first time. The EBIC images were correlated very well with transmission infrared (TIR) images of CZT crystals and the EBIC contrast was attributed to the nonuniformities in spatial distribution of Te inclusions. Further characterization by the thermally stimulated current (TSC) spectroscopy revealed shallow and deep level centers with activation energies 0.25- 0.4 eV and 0.65 - 0.8 eV respectively, which was attributed to intrinsic defects associated with Te inclusions. Pulse height spectra (PHS) measurements were carried out using ¹³⁷Cs (662 keV) radiation source and energy resolution of ~1.51% FWHM was obtained from the as-grown boule.