Vapor growth of CdTe laser window materials

Vapor deposition of CdTe from elemental cadmium and tellurium sources was studied as a function of the Cd/Te ratio, the supersaturation and the substrate temperature, in order to achieve optimum growth conditions for CdTe windows with low optical absorptivity in the infrared. A multisubstrate arrangement was designed to enable acquisition of growth data simultaneously on up to six specimens, each exposed to different growth conditions. Polycrystalline blanks up to 15 cm² × 2 mm thick were grown at rates of 0.02-1.5 mm/h with the growth rate exhibiting sensitivity to all of the above variables. Our results show that stoichiometry (as well as free carrier concentrations) can be controlled by adjustments in the Cd/Te ratio and/or the substrate temperature. Similarly, microstructural aspects (e.g., grain and void size) are shown to exhibit strong sensitivity to variations in growth conditions.