THE CHEMISTRY OF THE ORGANOMETALLIC VAPOR-PHASE EPITAXY OF MERCURY CADMIUM TELLURIDE

This review of the organometallic vapor-phase epitaxy (OMVPE) of mercury cadmium telluride examines the chemistry underlying film growth, film morphology, heteroepitaxy, doping, and reactor design. A key feature of the OMVPE of II-VI compounds, as distinguished from the OMVPE of III-V compounds, is that the intrinsic reaction kinetics control film growth. The rates of surface and gas-phase reactions determine the rate of deposition and the alloy composition. As a result, the quality of the material produced is very sensitive to the substrate temperature and the distribution of reactants in the gas above the substrate. Another crucial aspect of the growth chemistry is that cadmium telluride shows a strong tendency to grow in the (111) Te orientation. This makes it difficult to establish layer-by-layer growth on the (100), and instead films deposited on this surface are often covered with pyramidal hillocks. The orientation preference may be due to geometric constraints imposed by the rehybridization of the valence bonds of cadmium and tellurium upon incorporation into the crystal.