Local and anisotropic strain in AlN film on sapphire observed by Raman scattering spectroscopy

Abstract

Strain states in face-to-face-annealed sputter-deposited c-plane AlN (FFA-sp-AlN) films on c- and a-plane sapphire substrates were evaluated. As a result, an existence of anisotropic strain in the c-plane FFA-sp-AlN film on a-plane sapphire was ascertained by X-ray diffraction reciprocal space maps. Consequently, the peak splitting of polarized Raman spectra was observed from the c-plane FFA-sp-AlN film on a-plane sapphire for the first time. Meanwhile, there was no peak splitting of polarized Raman spectra of the c-plane FFA-sp-AlN film on c-plane sapphire, which has anisotropic strain. In addition, local and anisotropic strain relaxations in patterned FFA-sp-AlN films on c-plane sapphires were experimentally proven by polarized Raman spectra and two dimensional Raman spectra maps.