HARD HETEROEPITAXY OF MOLECULAR-BEAM EPITAXIAL GROWN PBTE ON OFF ORIENTED GAAS(100) SUBSTRATES

The geometrical model of the interface, GaAs(100) substrate surface an d PbTe, molecular beam epitaxial (MBE) layer was analyzed in order to explain the experimentally observed fact that PbTe layers of two orien tations, (100) and (111), may crystallize on the GaAs(100) substrate s urface. To our best knowledge the complete model of the PbTe/GaAs(100) interface has not been formulated so far. We have given here a first approximate construction of the PbTe/GaAs(100) interface, which allows us to explain why after the specific heat treatment of the GaAs subst rate prior to the MBE growth the (100), (111) or mixed PbTe epilayer o rientations are observed. We have shown that the best geometrical matc hing exists in the following cases: (a) PbTe(111)//GaAs(100) with a su rface lattice mesh of 23.984 X 3.997 Angstrom(2) (i.e. surface reconst ruction 6 x 1), which means a substrate surface with only few nucleati on centers; (b) PbTe(100)//GaAs(100) with a surface lattice mesh of 7. 99 x 3.997 Angstrom 2 (i.e. surface reconstruction 2 x 1), which means a substrate surface with an enhanced amount of nucleation centers. Th e first case occurs for a very carefully heat treated GaAs substrate s urface before the growth process is started, while the second one occu rs when the substrate platelet was heat treated at a lower temperature and far a shorter time, in comparison to the first case.