PHYSICAL VAPOR TRANSPORT OF CADMIUM TELLURIDE IN CLOSED AMPOULES

The dependence of the mass flux on the source material pretreatment, o n the source temperature, and on the temperature difference between th e source and transport product have been systematically investigated. Procedures have been developed yielding source materials of compositio n near that of the ''congruently vaporizing'' phase of CdTe. With this material, mass fluxes at moderate temperatures are observed which are up to about an order of magnitude larger than the highest reported in the literature for comparable conditions. Minute deviations from the ''stoichiometric'' composition reduce the mass flux by orders of magni tude. The experimental results are compared with theoretically predict ed mass fluxes based on a diffusion limited transport process, and wit h other possible limitations reported in the literature. The high mass fluxes observed in this work at relatively low temperatures enable th e vapor growth of large CdTe single crystals under conditions of pract ical importance.