Transmission electron microscopy was used to study ZnO grown by metal-organic vapor phase epitaxy on Al2O3(00•1) substrates. The defect structure of the material was dominated by an extraordinary high density of small stacking faults with extensions between 5 and 25nm which induced a bright small-scale speckle contrast under weak-beam imaging conditions. The stacking faults were terminated by Frank partial dislocations with Burgers vectors of the type 1/6 <2¯2•3>. The precipitation of interstitial atoms was the most likely process for the generation of the stacking faults, which were characterized by an additional (00•2) plane. The high stacking fault density could be considered as being an indicator of a high point defect concentration.

Origin and Consequences of a High Stacking Fault Density in Epitaxial ZnO Layers. Gerthsen, D., Litvinov, D., Gruber, T., Kirchner, C., Waag, A.: Applied Physics Letters, 2002, 81[21], 3972-4