Time of flight experimental studies of CdZnTe radiation detectors

Abstract

A time of flight technique was used to study the carrier trapping time, τ, and mobility, μ, 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 ∼500 nm. Signals from generated electrons 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 cm2/Vs to 2400 cm2/Vs between 293 K and 138 K, respectively. Electron mobilities were observed between 900 cm2/Vs and 1350 cm2/Vs at room temperature for various CZT detectors. Electron mobilities in various CdTe detectors at room temperature were observed between 740 cm2/Vs and 1260 cm2/Vs. Average electron mobility was calculated to be 1120 cm2/Vs and 945 cm2/Vs for CZT and CdTe, respectively. Hole mobilities in both CZT and CdTe were found to vary between 27 cm2/Vs and 66 cm2/Vs. Electron trapping times in CZT at room temperature varied from 1.60 µs to 4.18 µs with an average value of about 2.5 µs. Electron trapping time in CdTe at room temperature varied between 1.7 µs and 4.15 µs with an average value of about 3.1 µs.