Angular-Dependent Raman Study Of Alpha- And S-Plane Inn

Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar alpha-plane (1 (1) over bar 20) and semipolar s-plane (10 (1) over bar1) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A(1)(TO), E-1(TO), and E-2(h) on the angle psi that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and alpha-plane InN epilayers grown on nitridated r-plane sapphire (Al2O3) exhibit good crystalline quality as deduced from the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E-1(TO) and E-2(h) Raman peaks was used for the estimation of the strain state of the samples. (C) 2015 AIP Publishing LLC.