Accurate measurement of electrical bulk resistivity and surface leakage of CdZnTe radiation detector crystals

Abstract

A classical method for the accurate measurement of the bulk resistivity and a quantitative separation of bulk and surface leakage currents in semi-insulating CdZnTe radiation detectors is evaluated. We performed an extensive set of experiments on CdZnTe single-crystal test devices to confirm the reliability and reproducibility of the measurements and the validity of the underlying assumptions for data analysis and parameter extraction. The experiments included temperature dependent dual current-voltage measurements on devices with guard electrodes as a function of device thickness, surface preparation, surface passivation, and electrode deposition conditions. We also evaluated the temperature dependence of the bulk resistivity and implemented a general temperature normalization routine to allow a reliable comparison between various crystal samples.

Preliminary results of characterization of CdZnTe crystals grown by the Davidov-Markov method

“…This discrepancy could be connected to the low content of Zn in the study samples, as the band gap width depends on the Zn concentration and increases with its growth [12].…”

Conductivity type conversion in p-CdZnTe under pulsed laser irradiation

“…The wellknown methods based on Hall effect and thermoelectric current ("hot probe") measurements do not provide unambiguous results, which is caused by formation of the n-type conductivity layer at the surface of samples [8]. Moreover, correct measurements of the Hall effect require formation of the ohmic contact, which is problematic in p-type material.…”

“…Moreover, correct measurements of the Hall effect require formation of the ohmic contact, which is problematic in p-type material. Because of a low concentration and low mobility of holes in these materials, their product is small, causing an ambiguous interpretation of measuring results [8].…”

Study of effects of polishing and etching processes on Cd1−Zn Te surface quality

“…Bulk imperfections including impurities, vacancies, interstitials, grain boundaries, and dislocations have been relatively well studied and are known to trap charge and ultimately reduce detector performance [10]. Furthermore, mechanical damage induced by material processing or adsorbed chemical species on the surface is also known to trap charge or increase leakage current [11]. Rough or damaged surfaces exhibit persistent photoconductivity, which could be eliminated using chemical etching solutions [10].…”