A novel approach in voltage transient technique for the measurement of electron mobility and mobility-lifetime product in CdZnTe detectors

Abstract

In this study, a new measurement method based on voltage transients in CdZnTe detectors response to low energy photon irradiations is applied to measure the electron mobility (μe) and electron mobility-lifetime product (μτ)e in a CdZnTe detector.In the proposed method, the pulse rise times are derived from low energy photon response to 59.5 keV(241Am), 88 keV(109Cd) and 122 keV(57Co) γ-rays for the irradiation of the cathode surface at each detector for different bias voltages. The electron (μτ)e product was then determined by measuring the variation in the photopeak amplitude as a function of bias voltage at a given photon energy using a pulse-height analyzer. The (μτ)e values were found to be (9.6 ± 1.4)x10−3cm2 V−1 for 1000 mm3, (8.4 ± 1.6)x10−3cm2 V−1 for 1687.5 mm3 and (7.6 ± 1.1)x10-3 cm2 V−1 for 2250 mm3 CdZnTe detectors. Those results were then compared with the literature (μτ)e values for CdZnTe detectors.The present results indicate that, the electron mobility μe and electron (μτ)e values in CdZnTe detectors can be measured easily by applying voltage transients response to low energy photons, utilizing a fast signal acquisition and data reduction and evaluation. Keywords: CdZnTe, Electron mobility, Mobility-lifetime product, Transient pulse, Rise time, Charge Carrier, Digital pulse processing