Characteristics of stacking faults in AlN thin films

We have investigated growth characteristics and atomic structure of defects in AlN thin films grown by the metalorganic chemical vapor deposition technique on the (101̄2) r plane of α-Al2O3. The AlN films were single crystal and exhibited the following epitaxial relationship: (112̄0)AlN∥(101̄2)sap with the in-plane alignment of [0001]AlN∥[1̄011]sap. Using high-resolution electron microscopy and multislice image simulation, the predominant defects in AlN thin films grown on the r plane of α-Al2O3 were found to be low-energy intrinsic stacking faults of type I1 lying in the basal plane. This fault, with a 1/6[202̄3] resultant displacement vector, can be formed by removing one (0002) plane and then shearing the remaining half-crystal by displacement of 1/3[101̄0]. The faults appear as a single face-centered-cubic stack ABC inserted into the normal …ABAB… hexagonal sequence. We discuss the possible role of these defects in optical properties of semiconductor devices.