MOVPE growth of ZnSe and the effect of initiation conditions: a study by transmission electron microscopy

We have investigated the effect of the initial state of the GaAs substrate surface on the structural quality of ZnSe epilayers as grown by metal-organic vapour phase epitaxy (MOVPE). In contrast to the findings of many researchers using Molecular Beam Epitaxy (MBE), we have discovered that an extended exposure (15 min) of the GaAs substrate to a zinc flux (dimethylzinc in hydrogen) results in the formation of a well developed epitaxial Zn3As2 layer and that subsequent growth of ZnSe on this surface results in very high defect densities within the epilayer. This finding and other facts discussed herein indicate that the future direction for MOVPE of wide-gap ZnSe-related devices may be best served via homoepitaxy.