Boyang Wang a, Pengfei Yu a, Yuting Li a, Qingyang Xu a, Yize Zhang a, Wanqi Jie b
a School of Materials Science and Engineering, Chang'an University, Xi'an 710061, China
b State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
## Abstract
This study presents a comparative characterization of CdZnTe, CdMnTe, and CdMgTe single crystals, grown via a modified vertical Bridgman method, focusing on their structural, defect, optical, and electrical properties for room-temperature radiation detection applications. XRD analysis confirmed the sphalerite structure of all three crystals, with distinct preferred orientations influenced by spontaneous nucleation. CdMgTe crystal featured a lower density of Te inclusions (approximately 103 cm−2) compared to CdZnTe and CdMnTe. TEM analysis revealed all three crystals contained nanoscale Te precipitates, contributing to lattice distortion and dislocations. Compared to CdZnTe crystal, CdMnTe and CdMgTe exhibit better compositional uniformity. CdZnTe demonstrated superior crystal quality, with an average infrared transmittance of 62 % and a distinct free exciton peak in the photoluminescence spectrum. The resistivity of all three crystals met the specifications for room-temperature radiation detectors, with CdZnTe, exhibiting a resistivity of up to 7.09 × 1010 Ω·cm, showing the best detector performance.
## Introduction
Nuclear radiation detection materials and devices play a vital role in nuclear safety, industrial detection, medical imaging, space exploration, and other fields [[1], [2], [3]]. Among them, CdTe-based compound semiconductors, such as CdZnTe, CdMnTe, and CdMgTe crystals, are ideal candidates for room-temperature radiation detectors of X-rays, α particles, and gamma rays due to their suitable band gap, high resistivity, and excellent carrier transport characteristics [[4], [5], [6]]. CdZnTe crystals have been the most extensively studied and widely applied material for room-temperature radiation detection [7]. CdMnTe and CdMgTe crystals can be synthesized by substituting Zn in CdZnTe crystals with Mn and Mg elements, respectively. The segregation coefficients of Mn and Mg in CdTe are close to 1.0, allowing for a more uniform distribution of these elements in the ingot [8,9]. In the traditional vertical Bridgman (VB) method for growing CdTe-based crystals, Cd vacancies are easily produced due to the stoichiometric deviation caused by the high vapor pressure of the Cd element. However, the resistivity can typically be improved by a combination of impurity doping and deep level pinning [[10], [11], [12]], enabling their use in room-temperature radiation detectors. In this study, three detector-grade CdTe-based single crystals, namely CdZnTe, CdMnTe, and CdMgTe, were grown using a modified vertical Bridgman method under In-doped and Te-rich conditions. Combining excess Te with indium doping conditions can more effectively compensate for Cd vacancies, thereby reducing defects and increasing resistivity in CdTe-based crystals [13]. The structure, defect, optical, and electrical properties of these crystals were comparative characterization by X-ray diffraction, infrared transmission microscopy, high-resolution transmission electron microscopy, IR transmittance spectrum, Photoluminescence spectrum, current-voltage test and energy spectrum.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/structural-defect-and-photoelectric-characterization-of-cdte-based-single-crystals-grown-by-a-vertical-bridgman-method.html