Atomic rearrangement at the interface of annealed ZnSe films grown on vicinal Si(001) substrates.

Abstract

Significant atomic rearrangement at the interface was found to take place after post-growth annealing treatments of epitaxial ZnSe on As-passivated Si(001) substrates which were tilted by 4\ifmmode^\circ\else\textdegree\fi{} towards the [11\ifmmode\bar\else\textasciimacron\fi{}0] direction. The thermal stability of the ZnSe/As:Si interface was studied by rapid thermal annealing at temperatures up to 960 \ifmmode^\circ\else\textdegree\fi{}C after growing an epitaxial GaAs cap layer to prevent evaporation of the ZnSe during the anneals. The ZnSe/As:Si interface was examined by high-resolution electron microscopy. After an anneal at 900 \ifmmode^\circ\else\textdegree\fi{}C the ZnSe/As:Si interface transformed from an atomically smooth interface found in the as-grown films to a facetted structure with {111}-oriented sidewalls that extended preferentially in the [11\ifmmode\bar\else\textasciimacron\fi{}0] direction. The 60\ifmmode^\circ\else\textdegree\fi{} dislocations that were previously observed along this direc- tion combined into closely spaced pairs or into Lomer dislocations which were associated with the facets. We present a model for the atomic structure of the facetted interface which is consistent with the experimental data and satisfies electron-counting considerations. Total-energy calculations of the ZnSe/As:Si(001) interface were compared with those for the {111} interfaces seen after facetting.