Fundamentals of Crystal Growth from Vapors

Abstract

Crystallization from vapors has gained great importance in the preparation of epitaxial and polycrystalline layers of semiconductors, insulators and metals, as well as for the growth of some semiconductor bulk crystals. The vapor growth of bulk materials is typically conducted in closed or semi-closed systems. If the vapor pressure of a material at a desired growth temperature exceeds 10^-2 torr or so, it may be efficiently grown by Physical Vapor Transport, PVT (sublimation-condensation), Figure la. If the vapor pressure is too low for practical PVT rates, one may utilize a reversible reaction between the solid material and a gaseous “transport agent” that results only in volatile products, for Chemical Vapor Transport, CVT, Figure lb. The growth of solid layers, on the other hand, is typically conducted in open flow systems, either by Physical Vapor Deposition, PVD, Figure 1c, where the transport from the subliming source to the growth region is enhanced by a flowing carrier gas, or by Chemical Vapor Deposition, CVD, Figure 1d, where a reactive gas mixture is blown over a hot substrate. Occasionally, open flow systems have also been used for the growth of bulk crystals. There exists a large number of compilations of experimental techniques and theoretical models for these and other vapor growth processes in reviews [1–9] and proceedings of international conferences [10–15].