A novel "multi-tube" vapour growth system and its application to the growth of bulk crystals of cadmium telluride

A novel crystal growth apparatus which separates the source and growth regi ons of a vapour transport system into separate vertical furnaces connected by a horizontal transport passage has been developed. The transport passage incorporates a flow restrictor which regulates the mass flow and decouples it from the source-sink temperature difference. Growth takes place on a se ed crystal past which the growth envelope is dynamically pumped to ensure t hat the transport is diffusionless. This "multi-tube" arrangement offers se veral advantages over conventional linear vapour transport systems. In addi tion to control of the mass transport, source and growth regions are therma lly decoupled and there is noninvasive optical access to both source and cr ystal growth regions and for in situ vapour pressure monitoring. In this pa per, the results of in situ vapour pressure measurements made during the gr owth of a boule of cadmium telluride are presented and a flow model, which accounts for the significant molecular component of the transport, is devel oped and used to calculate the corresponding mass flows. This system offers the potential to give improved control of the nucleation and subsequent gr owth of large single crystals of high-vapour pressure opto-electronic mater ials such as the II-VI compounds. (C) 2000 Elsevier Science B.V. All rights reserved.