From Event: SPIE Optical Engineering + Applications, 2018
Cadmium Zinc Telluride (CdZnTe) is a good candidate for detection of x-ray and gamma-rays due to its high atomic number and large bandgap. CdZnTe is a II-VI group semiconductor and by changing ZnTe concentration, its properties can be altered. CdZnTe crystals having 4% ZnTe is commonly used as a substrate for Mercury Cadmium Telluride (HgCdTe) which is an important absorbing material for infrared imaging applications. For x-ray and gamma-ray detection, on the other hand, ZnTe concentration is kept around 10%. Due to high resistivity of CdZnTe crystals, preparation of surfaces prior to deposition of electrodes is important. After cutting and mechanical polishing, subsurface damages are observed on the crystals, which have a negative effect on the resistivity of the crystal near to the surface alongside with the dangling bonds on the surface. Decrease in the resistivity results in high leakage current that hinders the collection of electrons produced by absorption of photons. In addition, to have a strong bonding with electrode metal, surface should be clean from contaminants like oxygen and carbon. Achieving clean surface with low leakage current can be achieved by employment of chemical polishing step prior to electrode deposition. Bromine-alcohol solutions are used for chemical polishing without much control over the etching conditions. In this study, we report on the results of optimization study of chemical polishing by bromine-alcohol. Different alcohols (methanol, ethanol, propanol) were employed with different concentrations and etching durations. In addition, etching is conducted for different orientations to examine orientation dependency of the solution.
Mustafa Ünal, Deniz Bender, Özden Basar Balbasi, Merve P. Kabukcuoglu, Yasin Ergunt, and Rasit Turan, "Optimization of chemical polishing by bromine-alcohol for detector-grade CdZnTe crystals and its effect on contacts (Conference Presentation)," Proc. SPIE 10762, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XX, 107620U (Presented at SPIE Optical Engineering + Applications: August 21, 2018; Published: 18 September 2018); https://doi.org/10.1117/12.2323097.5836671676001.
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