CONTROLLING THE GROUP-II COMPOSITION IN CDZNTE ALLOYS GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY - A KINETIC-MODEL

The organometallic vapor phase epitaxy (OMVPE) of CdTe and ZnTe has be en examined in a hot-wall, laminar-flow reactor. It was found that cad mium and zinc are produced in excess on the film surface during OMVPE. The excess group II elements sublime off the surface and are deposite d downstream on the cold reactor walls. Based on these and other resul ts, a kinetic model has been derived for CdZnTe OMVPE. The elementary reactions included in this model are the adsorption of the organometal lic precursors, the desorption of the alkyl ligands, film growth, and the desorption of Zn and Cd metal. The predictions of the model have b een compared to the Zn segregation data reported in the literature. Th is analysis reveals that the distribution of the group II elements bet ween phases is relatively insensitive to the process conditions, i.e. temperature and VI/II ratio. However, it is strongly influenced by the intrinsic kinetic parameters, i.e. the difference in the Zn and Cd su blimation energies and the relative sticking probabilities of the orga nometallic precursors.