Investigation of deep levels in CdZnTeSe crystal and their effect on the internal electric field of CdZnTeSe gamma-ray detector

TL;DR

This study investigates deep levels in CdZnTeSe crystals using electrical and optical methods, revealing how selenium incorporation affects defect levels and the internal electric field in gamma-ray detectors.

Contribution

It introduces combined electrical and optical techniques to analyze deep levels in CdZnTeSe, providing new insights into defect behavior and material properties.

Findings

Se shifts the second ionization level of Cd vacancy towards the conduction band

Deep levels influence the internal electric field in CdZnTeSe detectors

Comparison with high-quality CdZnTe shows Se's impact on defect levels

Abstract

We present a study of deep levels in CdZnTeSe radiation-detection materials. The approach relies on electrical methods that combine time and temperature evolution of the electric field and electric current after switching on the bias voltage. We also applied two optical methods to study the deep levels. The first method utilizes the temperature and temporal analysis of the electric-field evolution after switching off an additional light illuminating the sample at a wavelength of 940 nm. The second method involved measuring of the electric-field spectral dependence during near infrared illumination. We compare the results with those obtained with high-quality CdZnTe detector-grade material. We conclude that the introduction of Se into the lattice leads to a shift of the second ionization level of the Cd vacancy towards the conduction band, as predicted recently by first-principles calculations based on screened hybrid functionals.