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Publikācija: Improvement of CdZnTe Crystal by Laser Radiation

Publication Type Conference paper
Funding for basic activity Unknown
Defending: ,
Publication language English (en)
Title in original language Improvement of CdZnTe Crystal by Laser Radiation
Field of research 1. Natural sciences
Sub-field of research 1.3 Physical sciences
Authors Artūrs Medvids
Aleksandrs Mičko
Edvīns Daukšta
Ernesto Diéguez
I. Crosso
H. Bensalah
Keywords CdZnTe Crystal, Laser Radiation
Abstract Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) semiconductor crystals have been shown to be the most promising materials for X-ray and gamma ray detectors due to high stopping power, low dark-current, high µe product, high room temperature band gap energy, high photosensitivity [1]. However, the yield of high quality crystal is still limited by some important problems, such as the presence of Te inclusions, crystal twins, grain boundaries, dislocations and other defects. A method for the annealing of CdZnTe crystal is used to improve the crystal quality [2]. Recently, several researchers have shown a possibility to improve crystal quality by CO2 laser irradiation [3, 4]. This method has disadvantages, such as long processing time about 100 h and damage of crystal surface. We have studied the influence of weakly absorbed Nd:YAG laser radiation on CdZnTe crystal electrical properties and radiation detector parameters [5].In the present work two type of CdZnTe crystals were used. The first type is crystal which was grown by vertical gradient freezing method using high-purity Cd, Zn and Te: 7N materials and doping with 3 ppm of Indium. Grown crystal is characterized by high concentration of non-controllable impurities and Te inclusions. The second type is crystal which was grown by high-pressure Bridgman method. Infrared microscopy was used to characterize CdZnTe samples, particularly concentration of Te inclusions. CdZnTe samples were irradiated by Nd:YAG laser and afterwards current voltage characteristic measurements were performed. Current voltage characteristic measurements showed that sample resistivity is increasing after irradiation by 700 laser pulses at intensity 6.6 MW/cm2. After this number of pulses, saturation effect can be observed and resistivity does not change anymore in the first type samples, but to the contrary - at the second type samples the negative photoconductivity effect was observed after irradiation by 7200 laser pulses at intensity 6.6 MW/cm2. It was observed that after irradiation by the laser dark current of the first type samples decreased by 40%. Measurements of γ-ray spectroscopy for the first type of CdZnTe crystal irradiated by the laser have shown the improvement of the energy spectral resolution. Therefore the quality of CdZnTe crystal is improved. References [1] T.E.Schlesinger, J.E. Toney, H.Yoon, YE.Lee, B.A. Brunett, L.Franks, R.B.James Materials Science and Engineering: R: Reports, 32(4/5), 103−189 (2001). [2] Guoqiang Li, Xiaolu Zhang, Hui Hua and Wanqi Jie, Semicond. Sci. Technol. 21, 392–396 (2006). [3] M.Meier, M.J.Harrison, S.Spalsbury, D.S.McGregor, Journal of Crystal Growth. 311, 4247-4250 (2009). [4] S.V Plyatsko, L.V.Rashkovetskyi, Semiconductors, 40, pp. 287-295 (2006). [5] A. Medvid‘,A.Mychko, E.Dauksta; V.Ivanov; E. Dieguzs, J.Crosso, H.Bensalah, IEEE Nuclear Science Symposium Conference Record , art. no. 6154756, 4672-4673 (2012)
Reference Medvids, A., Mičko, A., Daukšta, E., Diéguez, E., Crosso, I., Bensalah, H. Improvement of CdZnTe Crystal by Laser Radiation. In: The 6th International Meeting on Developments in Materials, Processes and Applications of Emerging Technologies (MPA 2012): Abstracts Book, Portugal, Alvor, 2-4 July, 2012. Alvor: 2012, pp.7-7.
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