Time of flight experimental studies of CdZnTe radiation detectors

A time of flight technique was used to study the carrier trapping time, tau , and mobility, mu, in CdZnTe (CZT) and CdTe radiation detectors. Carriers were generated near the surface of the detector by a nitrogen-pumped pulsed dye laser with wavelength similar to 500 nm. Signals from generated electr ons or holes were measured by a fast oscilloscope and analyzed to determine the trapping time and mobility of carriers. Electron mobility was observed to change with temperature from 1200 cm(2)/Vs to 2400 cm(2)/Vs between 293 K and 138 K, respectively. Electron mobilities were observed between 900 c m(2)/Vs and 1350 cm(2)/Vs at room temperature for various CZT detectors. El ectron mobilities in various CdTe detectors at room temperature were observ ed between 740 cm(2)/Vs and 1260 cm(2)/Vs. Average electron mobility was ca lculated to be 1120 cm(2)/Vs and 945 cm(2)/Vs for CZT and CdTe, respectivel y. Hole mobilities in both CZT and CdTe were found to vary between 27 cm(2) /Vs and 66 cm(2)/Vs. Electron trapping times in CZT at room temperature var ied from 1.60 mu s to 4.18 mu s with an average value of about 2.5 mu s. El ectron trapping time in CdTe at room temperature varied between 1.7 mu s an d 4.15 mu s with an average value of about 3.1 mu s.