Symmetrical Dipole Contribution from Planar Defects on m-plane ZnO Epitaxial Films

The planar defects such as basal stacking faults (BSFs) are probed on m-plane ZnO grown on LaAlO3(112) substrate by reflective second harmonic generation (RSHG). The BSFs result in nonvanishing single-direction dipoles that behave similar to a mirror-like symmetrical dipole. The RSHG pattern from m-plane ZnO comprised of not only the bulk dipole contribution of ZnO but also an additional mirror-like symmetrical dipole contribution from BSF defects. Transmission electron microscopy image displays the presence of BSFs that lie in the c-plane of ZnO and agrees well with RSHG results. Planar BSFs are formed due to the anisotropic stress relaxation between m-plane ZnO film and LaAlO3(112) substrate, resulting in higher-quality m-plane ZnO films.