Charge transport properties in CdZnTeSe semiconductor room-temperature γ-ray detectors

摘要

Cd_xZn_(1-x)Te_ySe_(1-y) (CZTS) has emerged as a next-generation compound semiconductor for high energy gamma-ray detection. In the present study, we report for the first time the hole transport property measurements in CZTS based gamma-ray detectors in the planar configuration. Current-voltage measurements revealed a bulk resistivity of ~5 × 10~8 Ω cm and the fabricated detectors produced well-resolved 5486 keV alpha particle peaks, for both electrons and holes drifting alike, when pulse-height spectra (PHS) were recorded using a ~(241) Am radiation source. The PHS measurements were enabled to measure the charge transport properties for both the charge carriers. The mobility-lifetime product (μτ) for electrons and holes was calculated to be 6.4 × 10~(-4) cm~2 V~(-1) and 8.5 × 10~(-5) cm~2 V~(-1), respectively, using a single polarity Hecht plot regression method. The pre-amplifier pulses were also recorded and processed digitally to obtain electron and hole drift mobilities of 692 cm~2 V~(-1) s~(-1) and 55 cm~2 V~(-1) s~(-1), respectively, using a time-of-flight method. The measured transport properties indicated the hole lifetime to be greater than the electron lifetime by a factor of ~1.5. Gamma-ray PHS were recorded using fabricated detectors that showed tailing of the 662 keV photopeak due to hole trapping effects. Depth dependent PHS were digitally generated from 2D biparametric plots to reveal the effects of hole trapping on the gamma PHS at different detector depths. Digital correction procedures were applied to generate well-resolved PHS with an energy resolution of ~2% for 662 keV γ-rays.