Hard heteroepitaxy of molecular beam epitaxial grown PbTe on off oriented GaAs(100) substrates

Abstract

The geometrical model of the interface, GaAs(100) substrate surface and PbTe, molecular beam epitaxial (MBE) layer was analyzed in order to explain the experimentally observed fact that PbTe layers of two orientations, (100) and (111), may crystallize on the GaAs(100) substrate surface. To our best knowledge the complete model of the PbTeGaAs(100) interface has not been formulated so far. We have given here a first approximate construction of the PbTeGaAs(100) interface, which allows us to explain why after the specific heat treatment of the GaAs substrate prior to the MBE growth the (100), (111) or mixed PbTe epilayer orientations are observed. We have shown that the best geometrical matching exists in the following cases: (a) PbTe(111)//GaAs(100) with a surface lattice mesh of 23.984 × 3.997 Å2 (i.e. surface reconstruction 6 × 1), which means a substrate surface with only few nucleation centers; (b) PbTe(100)//GaAs(100) with a surface lattice mesh of 7.99 × 3.997 Å2 (i.e. surface reconstruction 2 × 1), which means a substrate surface with an enhanced amount of nucleation centers. The first case occurs for a very carefully heat treated GaAs substrate surface before the growth process is started, while the second one occurs when the substrate platelet was heat treated at a lower temperature and for a shorter time, in comparison to the first case.