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

Atomic-layer epitaxy (ALE) processes of ZnSe on GaAs(001) have been studied using reflection high-energy electron diffraction (RHEED), total reflectio n-angle x-ray spectroscopy, and x-ray photoelectron spectroscopy. We have o btained direct evidence that the growing surface of ZnSe(001) changes its c hemical composition during ALE growth, which corresponds to the alternate f ormation of the Se-stabilized (2 x 1) and Zn-stabilized c(2 x 2) reconstruc tions. The rocking-curve analysis of RHEED have been used in structure anal ysis for these reconstructed surfaces: the (2 x 1) surface has the Se-dimer structure, in agreement with previous studies. On the other hand, we have found that the c(2 x 2) surface has the Se-vacancy structure, contrary to t he previously proposed Zn-vacancy structure. The growth rate of ZnSe has be en estimated to be about 0.5 bilayer per ALE cycle, which is consistent wit h the formation of these surface structures. [S0163-1829(99)13235-1].