Silicon-germanium bulk alloy growth by liquid encapsulated zone melting

Abstract

The present invention describes the growth of single crystals of non-congruently melting alloys, in particular, silicon-germanium of constant composition in a quartz ampoule by the use of CaCl.sub.2 as an encapsulant for the liquid encapsulated zone melting (LEZM) technique. The zone melting process was modified with the addition of calcium chloride which acts as a liquid encapsulant at temperatures above 660.degree. C. so that the crystal can grow without sticking to the container. The calcium chloride encapsulant creates a non-wetting buffer layer between the quartz container and the SiGe charge material allowing single crystal growth of mixed alloys. The crystal growth system consists of a vertical tube RF furnace with a water cooled split-ring concentrator. The concentrator is 5 mm. Thick by 25 mm diameter and provides a high temperature melt zone with a "spike" profile. The single crystal seed and the polycrystalline alloy charge are loaded into a quartz ampoule which fits freely through the concentrator coil. The encapsulant calcium chloride is placed on top of the charge so that when it melts, it covers the inner surface of the quartz ampoule. During operation the alloy charge is melted in the "spike" zone at the seed interface, and then the molten zone is translated along the length so that a single crystal of uniform composition is formed.

Dependencies are inferred from the claim text.