Striated surface morphology and crystal orientation of m-plane GaN films grown on γ-LiAlO2(100)

Abstract

Polarized in-plane and cross-sectional Raman spectra have been used to determine the crystal orientation of m-plane GaN grown on $\gamma {\text{-LiAlO}}_2\left(100\right)$ (LAO) using a three-step metalorganic vapor phase epitaxy process. The epitaxial relationship is found to be $\text{GaN}\left(1\overline{1}00\right)\parallel \text{LAO}\left(100\right)$ and $\text{GaN}\left[11\overline{2}0\right]\parallel \text{LAO}\left[001\right]$ . However, the stripes on the GaN surface are oriented parallel to [0001], i.e., perpendicular to the one found on striated m-plane GaN surfaces in previous studies. This unusual orientation is attributed to the changes in the Ga adatom kinetics due to the presence of a 2-nm-thick interlayer observed at the GaN/LAO interface in transmission electron microscopy.