Nucleation and growth kinetics of II-O epitaxial layers deposited on 6H–SiC substrates

Nucleation and growth kinetics of II-O epitaxial layers deposited on SiC substrates have been investigated. ZnO nucleates initially with islands and switches to coalescences and grains with the increase of layer thickness, while MgxZn1−xO alloys grow with two-dimensional growth mode. The strain kinetics due to the driving force Δa/a favors the coherent growth of ZnO for the layer thickness of <6 nm and start to relax afterwards, while the MgxZn1−xO alloys relax slowly with the increase of Mg content. Although the atomic radii of Mg+2 (0.57 Å) and Zn+2 (0.60 Å) cations are close, the Mg composition uncertainty was found in between Vegard’s law and experiment to be ∼3%. This has been attributed to the atomic relaxation in ZnO/MgO structure due to the lattice misfit of ∼2%, together with the inhomogeneous potential fluctuations locally in the MgxZn1−xO alloys.