Fabrication and Characterization of ${\rm Cd}_{0.9}{\rm Zn}_{0.1}{\rm Te}$ Schottky Diodes for High Resolution Nuclear Radiation Detectors

Abstract

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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm Cd}_{0.9}{\rm Zn}_{0.1}{\rm Te}$</tex></formula> detector grade crystals grown from zone refined Cd, Zn, and Te (7N) precursor materials using low temperature tellurium solvent method. Various crystallographic defects including Te-inclusions/precipitates were identified and characterized using electron beam induced current (EBIC) measurement and thermally stimulated current (TSC) spectroscopy. The EBIC images were correlated with transmission infrared (TIR) images of CZT crystals and the EBIC contrast was attributed to the nonuniformities in spatial distribution of Te inclusions. Characterization by TSC revealed shallow and deep level centers with activation energies 0.25–0.4 eV and 0.65–0.8 eV respectively, which were attributed to intrinsic defects associated with Te inclusions. Pulse height measurements were carried out using <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{137}{\rm Cs}$</tex></formula> (662 keV) radiation source and energy resolution of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim 1.51}\%$</tex></formula> full width at half maximum (FWHM) was obtained from the as-grown boule.