JSC “Giredmet”, Moscow, Russia:

M. B. Grishechkin, Researcher
I. A. Denisov, Head of Laboratory, e-mail: IADenisov@rosatom.ru
A. A. Silina, Researcher
N. I. Shmatov, Senior Researcher

Presented are the research results of cadmium-zinc-tellurium crystals no less than 60 mm in diameter growing by vertical Bridgman method (VBM) under conditions of spontaneous melt crystallization at the initial stage of a solid phase formation. It has been established that discontinuity of protective coating on an ampoule internal surface leads to a drop in the single-crystal wafers yield. Use of a glass-carbon tube for eliminating melt contacts with quartz walls of the ampoule has allowed to improve structural perfection of the grown crystals. Defined are the processes realization conditions which can guarantee obtaining of ingots with a volume of monocrystalline area, suitable for manufacturing substrates with the surface orientation parallel to crystallographic planes (111) and (211) no less than 50 mm in diameter with homogeneous distribution of dislocations and of density no more than 8·10⁴ cm^–2, without low-angle boundaries. Values of optical transmission coefficient in a spectral range from 2.5 to 20 μm comprise no less than 60%. There was fulfilled an optimization of substrate plates mechanical polishing modes for different choices of polishing pad material with the use of suspensions based on aluminium, ceric and silicon oxides of diverse grain. The best results have been achieved in case of suspensions based on aluminium oxide. Surface roughness of substrate plates, estimated by an arithmetical mean deviation of a profile (R_a) is of the order of 4.5 nm for Al₂O₃ with a 0.05-μm grain and of 6 nm for Al₂O₃ with a 0.3-μm grain, while an average scratch depth doesn’t exceed 18 and 40 nm, respectively. Deviation from flatness of profile of substrate plates up to 50 mm in diameter comes to ~0.5 μm after mechanical and the subsequent chemical mechanical polishing. Examination of surface areas of the plates by infrared microscopy has revealed a complete elimination of damages caused by mechanical polishing after stripping of 10–15 μm by chemical mechanical method.

This work was carried out with the financial support of the Ministry of Education and Science of the Russian Federation in the framework of the Agreement on subsidies No. 14.576.21.0055 of October 21, 2014 (Unique identifier: RFMEFI57614X0055).

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