Crystal growth and characterization of Cd0.9Zn 0.1Te for gamma-ray detectors: thermally stimulated current (TSC), electron beam induced current (EBIC), and pulse height spectroscopy (PHS)

Abstract

Cd0.9Zn0.1Te (CZT) detector grade crystals were grown from in-house zone refined Cd, Zn, and Te (7N) precursor materials, using a low temperature tellurium solvent growth method. These crystals were grown using a high temperature vertical furnace designed and installed in our crystal growth laboratory at the University of South Carolina (USC). The furnace is capable of growing up to 8″ diameter crystals. Custom pulling and ampoule rotation using custom electronics were developed for this crystal growth setup. CZT crystals were grown using excess Te as a solvent with growth temperatures lower than the melting temperatures of CZT (1092 °C). Tellurium inclusions were characterized through IR transmission maps for the grown CZT ingots. The crystals from the grown ingots were processed and characterized through I-V measurements for electrical resistivity. Defect levels are evaluated through thermally stimulated current (TSC) and electron beam induced current (EBIC) measurements. Pulse height spectra measurements were carried out using 241 Am (60 keV) and 137 Cs (662 keV) radiation sources. Our investigations demonstrated high quality nuclear detector grade CZT crystals growth using this low temperature Te-solvent method.