A study of surface and interlayer structures of epitaxially grown group-III nitride compound films on Si(111) substrates by second-harmonic generation

Abstract

The symmetry behaviour of AlN/Si(111) and GaN/AlN/Si(111) structures grown by molecular beam epitaxy has been analysed by measuring the rotational dependence of the polarized second-harmonic generation (SHG) intensity for different polarized fundamental beams. The crystalline structure has also been checked by reflection high-energy electron diffraction, x-ray diffraction and photoluminescence spectroscopy. Considering various contributions of the nonlinear response from the bulk and interfaces, the interface strain implies an inhomogeneous intensity variation of SHG as a function of the surface azimuthal rotation angle Ψ. This result provides a valuable illustration of the epitaxy quality and growth parameter characterization by a nondestructive method.