Synchrotron radiation x-ray absorption fine-structure and Raman studies on CdZnTe ternary alloys

Abstract

The synchrotron radiation (SR) X-ray absorption fine-structure spectroscopy (XAFS) technology has been employed to obtained Zn K-edge absorption spectra for Cd 1−x Zn x Te alloy with x = 0.03, 0.10, 0.20, 0.30, 0.40, 0.50 and 1.00. Their Fourier transform spectra were analyzed, which have shown a bimodal distribution of bond lengths, suggesting distortion of the Te sub-lattice, so that the linear interpolation is true only in an approximate sense. Synthetic CdZnTe crystals can be used for the room temperature-based detection of gamma radiation. The radiation detection properties of CZT crystals vary widely. A common defect found in most high-quality CZT crystals is Te secondary phases, often located along grain boundaries. The secondary phases can be both large inclusions (>50 μm) and smaller precipitates (<50 μm). The Te secondary phases distributed throughout the crystal can cause changes to the detector leakage current, resulting in decreased radiation spectrometer performance. This set of Cd 1-x Zn x Te crystals were also measured by Raman scattering at room temperature. The two observed peaks at about 125 and 145 cm -1 which can be assigned to Te A 1 and E phonon mode, respectively. The induced damage on the crystal surfaces by Raman laser has been discussed. It is suggested that in the case of highly Zn doping CdZnTe crystals, the ZnTe bond were broken by laser exposing and then free Te atoms are migrating to these heated areas which cause Te precipitate. Further, the results of the soft X-ray measurements have been also presented and this part of the experimental data needs to do more penetrating analysis in the future.

Composition dependence of structural and optical properties of Cd1−Zn Te thick films obtained by the close-spaced sublimation

“…We assume that the appearance of the strong Te-related modes is caused by local heating of the sample surface, as this was shown in [75,77,78]. This assumption was confirmed by RS measurement using 633 nm excitation wavelength.…”

“…The energy of green or blue wavelength radiation is much higher than BG of CdTe or Zn-poor CZT and hence, the high absorbance of excitation radiation occurs. In this case, the penetration depth of the green wavelength radiation for CdTe and ZnTe is only 200 and 400 nm, respectively [75]. Thus, the excitation light is absorbed in a thin near-surface layer that could lead to local heating of the material followed by Te enrichment on the surface, even at low green laser excitation power [75,77,78].…”

“…In this case, the penetration depth of the green wavelength radiation for CdTe and ZnTe is only 200 and 400 nm, respectively [75]. Thus, the excitation light is absorbed in a thin near-surface layer that could lead to local heating of the material followed by Te enrichment on the surface, even at low green laser excitation power [75,77,78]. In order to determine the position of Te-related modes, the tellurium crystal was measured as a reference, using three available laser excitations wavelengths.…”

“…The green excitation with a high energy is often used for the Raman study of the CdTe and CZT samples with low Zn concentration [33,75,76]. The energy of green or blue wavelength radiation is much higher than BG of CdTe or Zn-poor CZT and hence, the high absorbance of excitation radiation occurs.…”

TCAD simulation of a proposed 3D CdZnTe detector

“…Cadmium telluride (CdTe), zinc telluride (ZnTe) and cadmium zinc telluride (CdZnTe) are the most semiconductor materials that have obtained significant attention as X‐ray and ‐ray detectors because of their low leakage current and high detection efficiency at room temperature [2]. These compounds have a lot of applications including optoelectronics, microelectronics, sensor electronics and photovoltaics [3–5].…”