GROWTH OF LARGE, HIGH-PURITY, LOW-COST, UNIFORM CDZNTE CRYSTALS BY THE COLD TRAVELING HEATER METHOD

The cold travelling heater method (CTHM) has been used to grow CdZnTe crystals (x(Zn) = 0.04 and 0.20) of 2 inch diameter, which is the largest diameter ever used in THM. A simple model confirms that convection is the dominant mechanism of matter transport in THM, justifying the use of the accelerated crucible rotation technique (ACRT), in which is imposed a forced convection regime, to enlarge the size of the crystals and increase the growth rate. In order to obtain single crystals, solid state recrystallization (SSR) has been applied for the first time to CdTe. Ingots of excellent axial and radial uniformity have been obtained by CTHM, as well as crystals purer than the Bridgman grown ones, from 5N elements as source material at ten times lower price than the 6N ones classically used for Bridgman growth. SSR crystals have been found also of lower purity than the CTHM ones. It follows that contamination in CdTe growth is expected to occur not only from the starting elements but particularly from the high temperatures used. The main agents of high temperature contamination are shown to be Li and Cu. Some mosaic structure of the crystals comes from the off-stoichiometric THM growth conditions and could be avoided by SSR annealing under Cd vapour pressure.