METHOD OF PRODUCING CDTE CRYSTAL FOR ELECTROOPTICAL MODULATORS Russian patent published in 2025 - IPC C30B29/48 C30B9/06 C01B19/04 C01G11/00 G02F1/03 

FIELD: chemistry.

SUBSTANCE: invention can be used in making electrooptic devices at wavelength. To obtain high-purity elementary cadmium and tellurium, they are pre-purified to 7N purity by, at least, triple distillation in vacuum with residual pressure of 0.1 Pa. at temperature of about 320 °C for cadmium and at a temperature of about 450 °C for tellurium and subsequent additional triple directed crystallisation of tellurium at temperature of about 450 °C. High-temperature synthesis of a charge of cadmium telluride from the obtained high-purity elementary cadmium and tellurium with excess elementary tellurium at its content in charge of 60-70 atm.% is carried out for 4 hours in an evacuated quartz container made in the form of a conical ampoule, which is placed in a two-zone horizontal furnace, at a temperature of the "hot" zone of 900-720 °C and "cold" zones 680-500 °C. Then the synthesized charge of cadmium telluride and the seed crystal of CdTe are placed in the vertex of the cone of the evacuated quartz conical ampoule, which is placed in a double-zone furnace equipped with a diaphragm for vertical directed crystallisation of CdTe on the said oriented seed from the melt solution. Thereafter, the mixture is heated to melting point. In the lower zone – in the crystallization zone, a vertical temperature gradient of 1.8-2.0 °C/mm, in the upper zone – in the zone of the solution-melt, low-gradient conditions are created with a temperature gradient of 0.1-0.5 °C/mm. Ampoule is lowered into the lower zone at rate of 4-5 mm/day. In the process of crystallization, the temperature of both zones is synchronously reduced, while the temperature reduction rate provides a nonlinear, close to hyperbolic, nature of temperature change, which varies from 0.1°/h at the beginning of crystallisation up to 1-3°/h at the end of crystallization for 15 days, creating conditions for stabilization of the solid-liquid interface. After crystallisation, the obtained CdTe crystal is cooled at rate of 5-6 °C/h.

EFFECT: invention enables to obtain CdTe crystals up to 50 mm in length and up to 35 mm in diameter with high optical transmission at wavelength of 10.6 mcm, equal to 0.01 cm^-1, and low density of extended and point defects.

1 cl, 1 tbl, 3 ex