Kinetics of the Vapor Growth of II-VI Compounds Crystals

Abstract

Theoretical and experimental studies have been made of the vapor growth of the II-VI compound crystals by a modified Piper method. As a typical example, single crystals of cadmium sulphide have been grown and the growth rates observed on various conditions. It has been found that the rate is approximately proportional to the inverse of argon pressure in its atmosphere and considerably suppressed by an excess vapor of the constituent element, in particular, cadmium. Growth kinetics for the II-VI compound crystals has been developed on the basis of the mechanism that the growth proceeds via three steps: vaporization of the source material, diffusion of the vaporized species, and condensation onto the crystal surface. The theoretical formulas thus obtained have quantitatively well reproduced the experimental results. It has been concluded that the rate-determining step is the diffusion of the vaporized species. An examination of the vapor pressure has revealed that this condition is necessary for the growth of large single crystals, together with a temperature profile sublinear along the crucible axis.