Structure and composition of the ZnSe(001) surface during atomic-layer epitaxy

Abstract

Atomic-layer epitaxy (ALE) processes of ZnSe on GaAs(001) have been studied using reflection high-energy electron diffraction (RHEED), total reflection-angle x-ray spectroscopy, and x-ray photoelectron spectroscopy. We have obtained direct evidence that the growing surface of ZnSe(001) changes its chemical composition during ALE growth, which corresponds to the alternate formation of the Se-stabilized $(2\ifmmode\times\else\texttimes\fi{}1)$ and Zn-stabilized $c(2\ifmmode\times\else\texttimes\fi{}2)$ reconstructions. The rocking-curve analysis of RHEED have been used in structure analysis for these reconstructed surfaces: the $(2\ifmmode\times\else\texttimes\fi{}1)$ surface has the Se-dimer structure, in agreement with previous studies. On the other hand, we have found that the $c(2\ifmmode\times\else\texttimes\fi{}2)$ surface has the Se-vacancy structure, contrary to the previously proposed Zn-vacancy structure. The growth rate of ZnSe has been estimated to be about 0.5 bilayer per ALE cycle, which is consistent with the formation of these surface structures.