Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

Abstract

The m-plane GaN films grown on LiAlO2(100) by metal-organic chemical vapor deposition exhibit anisotropic crystallographic properties. The Williamson–Hall plots point out they are due to the different tilts and lateral correlation lengths of mosaic blocks parallel and perpendicular to GaN[0001] in the growth plane. The symmetric and asymmetric reciprocal space maps reveal the strain of m-plane GaN to be biaxial in-plane compress εxx=−0.79% and εzz=−0.14% with an out-of-plane dilatation εyy=0.38%. This anisotropic strain further separates the energy levels of top valence band at Γ point. The energy splitting as 37meV as well as in-plane polarization anisotropy for transitions are found by the polarized photoluminescence spectra at room temperature.