Maznytska O. The improvement of the arsenic metal technology with reduced oxygen content for the preparation of monocrystals of GaAs

Object - technological processes of preparation of high purity arsenic metal with reduced oxygen content for the electronic application (for production of monocrystals of GaAs). Aim - the improvement of industrial technology of cleaning AsCl3 and its reduction for the receipt of metallic arsenic with the lowered maintenance of oxygen. Methods - fundamental positions of chemical thermodynamics and kinetics, theory of division of matters in phases transitions, physics of semiconductors, physical and chemical bases of processes of distillation and rectification. Results - were determined the optimal values of the technological parameters of the rectificative purification of AsCl3 from the oxygen impurities in HCl atmosphere and, in addition, the optimal conditions (temperature, hydrogen excess) of the arsenic chloride reduction process into arsenic metal also were found; the existing technology of the arsenic metal preparation comprises the chlorination of As2O3 with aqueous HCl to furnish AsCl3, the rectification of, and the following reduction of the last one (AsCl3) into arsenic metal with hydrogen. It has been found that in this case the main source of oxygen, which contaminates the final compound, is the products of hydrolysis of AsCl3 (oxychlorides). To prevent the hydrolysis has been suggested to feed the rectifying column with HCl gaseous. The synthesized arsenic metal meets the quality of the 7N standard. The grown monocrystals have perfect electrophysical parameters (for undoped samples: n = 4·1014, mobility µ = 8,03·103 cm/V·s; for compensated samples: specific resistance p = 1,21·108 Om ·cm, µ = 6,108·103 cm/V·s). Innovation - new method and equipment for removing of the oxygen impurities have been developed. And the quarts reactor to reduce AsCl3 into a hydrogen flow under optimal conditions has been also constructed. Field of implementation - the improved technology is implemented on the enterprise at the stock company "Pure Metals Plant" and in an educational process at the study of some courses. Sphere of implementation - electronic industry enterprises and branch research institutions dealing with monocrystals of GaAs grows.