Metalorganic Chemical Vapor Deposition and Characterization of Epitaxial MgxZn1-xO (0 <= x <= 0.33) Films on (0112)r-Sapphire Substrates

In this work, MgxZn1-xO (0 = x = 0.33) thin films are epitaxially grown on (0112)r-sapphire substrates by metalorganic chemical vapor deposition. A thin ZnO buffer layer in the order of 50 Angstrom is found to be critical for the growth of single crystal MgxZn1-xO (0 = x = 0.33) films with a wurtzite-type structure. The energy bandgap of MgxZn1-xO films as a function of Mg composition was deduced using a UV-Visible spectrophotometer at room temperature in conjunction with Rutherford Backscattering Spectroscopy measurements. The epitaxial relationship between the wurtzite-type MgxZn1-xO films and r-sapphire substrates is determined to be (1120) MgxZn1-xO || (0112) Al2O3, and [0001] MgxZn1-xO || [0111] Al2O3. In-plane X-ray diffraction reflections show the lower lattice mismatch along the c-axis of the MgxZn1-xO films on r-sapphire substrates. High resolution transmission electron microscopy analysis of the film substrate interface indicates the region in the film near the interface is crystalline though strained.