Cd$_{0.9}$ Zn$_{0.1}$ Te Crystal Growth and Fabrication of Large Volume Single-Polarity Charge Sensing Gamma Detectors

Detector grade Cd
_0.9
Zn
_0.1
Te single crystals were grown using a tellurium solvent method. Single crystal blocks of volume ~1 cm
³
were prepared for detector fabrication and characterization. The grown crystals were characterized using infra-red transmission imaging and Pockel's effect measurements. Two detectors in single-polarity charge sensing configurations viz., small pixel, and virtual Frisch grid were fabricated on two crystals obtained from the same section of the ingot. Current-voltage measurements performed in planar configuration exhibited a very low leakage current of ~5 nA at 1000 V and resistivities of the order of 8.5×10
¹⁰
Ω·cm. Electron drift mobilities of the order of 840 cm
²
/V.s and electron mobility-lifetime products of the order of 2.7×10
^-3
cm
²
/V were calculated from alpha spectroscopy using detectors in planar configuration. The small pixel and the virtual Frisch grid detector showed similar energy resolution of 3.7% for 662 keV gamma rays however, the virtual Frisch grid configuration revealed a better overall performance with a peak-to-Compton ratio of 2.8. A digital spectrometer and related software has been developed using a digitizer card and used to employ offline correction schemes to compensate for the charge loss effects, resulting in significant improvement of the 662 keV peak resolution (1.8% as compared to 3.7% without correction) obtained in the case of small pixel detector.