An experimental and modeling analysis of vapor transport deposition of cadmium telluride

Vapor transport deposition (VTD) was employed for high-rate deposition of CdTe thin film solar absorbers. A detailed model was developed for CdTe deposition that included the role of source conditions, convective mass transport, and deposition chemistry. A Langmuir formulation that was consistent with experimental observations of resublimation was used to describe the surface reaction probability. Comparisons of experiment and model showed very good agreement over a range of operating conditions. The model predicts an optimum operating pressure for VTD, arising from a competition between surface kinetics and dilution of the precursor species. For VTD deposition of CdTe the optimum pressure is in the range of 2–5 Torr. These modeling concepts may be easily extended to VTD of other materials as well.