Raman analysis of anisotropic strain in semipolar (112¯2) AlN grown on m-plane sapphire

The anisotropic strain characteristics of semipolar (112¯2) AlN grown on m-plane sapphire were investigated by Raman spectroscopy and high-resolution x-ray diffraction. The Raman quasi-TO mode exhibited a systematic asymmetry in the line shape, which was quantified by the asymmetry factor β using bi-pseudo-Voigt fitting. XRD analysis of multiple diffraction planes confirmed the presence of anisotropic strain in the films. A monotonic correlation was found between β and the anisotropic strain parameter (εaa−εam) derived from XRD. These results suggest Raman β-factor analysis can serve as a practical, nondestructive indicator of anisotropic strain in semipolar (112¯2) AlN.