Nucleation processes during metalorganic vapor phase epitaxy of ZnSe on GaAs(001)

We investigate the nucleation processes of ZnSe grown on GaAs(001) by metalorganic vapor phase epitaxy (MOVPE). The growth of ZnSe begins with an initial exposure of GaAs to either a Zn or a Se precursor. The Zn-initiated growth initially develops through formation of anisotropic two-dimensional (2D) islands and then exhibits a transition to 2D layer-by-layer growth. In the Se-initiated growth, on the other hand, the initial 2D islands are isotropic and the thickness at which the growth mode changes to the layer-by-layer mode is thicker than that in the Zn-initiated growth. Three-dimensional growth does not occur in the present MOVPE, which is remarkably different from molecular beam epitaxy. The observed variation of the nucleation is explained in terms of the interface structures. On thick ZnSe layers, where the growth is free from the influence of the interface, several stages during 1 monolayer formation through 2D layer-by-layer growth are clearly observed. (C) 1998 American Institute of Physics.