Structural and Optical Properties of Nonpolar $(11 \bar{2}0)$ ZnO Films Grown by Plasma-Assisted Molecular-Beam Epitaxy

Structural and optical properties of ZnO epilayers grown on
$r$
-plane sapphire substrates by plasma-assisted molecular-beam epitaxy have been investigated using various techniques. A high-purity wurtzite structure and a smooth surface with an
$a$
-plane orientation were obtained. The resonant Raman scattering spectra show a typical multiphonon vibration characteristic from wurtzite ZnO. A good near band gap luminescence property is revealed in photoluminescence spectra.