COMPARISON OF HGTE MATERIALS GROWN IN (100), (110), (111), AND (211) ORIENTATIONS

We calculated energies required to remove atoms from various configura tions on (111), (110), (100), and (211) HgTe surfaces. The excess pair energies for various species are then calculated and are used in a th ermodynamic model to study the growth. All energies are obtained using a Green's function method. The pair distributions are calculated from these energies in a generalized quasi-chemical approximation. The cal culated critical temperatures for surface roughness transition are fou nd to be considerably higher than the usual growth temperature of 185 degrees C, so the growth on these surfaces is expected to be layer-by- layer with formation of two-dimensional islands. However, among the su rfaces studied, only the (211) surfaces have an attractive binding ene rgy for Hg, making those surfaces suited for better growth. The critic al temperature for growth on (211)Hg is slightly higher than that for (211)Te, but we also find that Hg sticking coefficient on (211)Hg surf ace is considerably lower than that on (211)Te surface. These calculat ions are consistent with the observed higher growth rate of the (211)T e surface. Our calculations suggest that there will be fewer grown-in vacancies and Te antisites, at the expense of growth rate and sticking coefficient, for crystals grown on (211)Hg surface. We further calcul ated the Hg and Te vacancy formation energies as functions of surface orientations and layer depth. The cation vacancy formation energies fr om completed surface regions (islands) are higher than bulk values nea r anion terminated surfaces and smaller than bulk values near cation t erminated surfaces.