Estimation of solid-vapor distribution coefficients in organometallic vapor phase epitaxy of II–VI semiconductors

Abstract

We use equilibrium thermodynamics to explain non-linear alloy incorporation in the organometallic vapor phase epitaxy (OMVPE) of ternary II–VI compounds such as ZnSe x S 1 − x and Hg 1 − x Cd x Te. Our analysis includes the effects of incomplete decomposition of gas phase reactants as well as non-ideal solution effects in the product film. As an extension of our discussion of the specific II–VI systems above, we derive general formulas which can be applied to any OMVPE system for the limiting cases of complete or absent anion reactant decomposition. These formulas, which assume small dissociation for the solid films, replace the complicated procedure of free energy minimization with direct calculation of entire solid-vapor distribution curves. The parameters involved are temperature, the solid solution interaction parameter, the initial VI/II ratio, and the ratio of dissociation constants for the binary components of the solid film. This approach also allows us to anticipate systems in which kinetic effects may be important, based on the observation of thermodynamically unpredicted results.