Raman scattering in InN films and nanostsructures

Studies of lattice dynamics devoted to wurtzite InN are presented. Raman scattering experiments on both InN thin films and nanometric islands grown by Metal-Organic Vapor Phase Epitaxy (MOVPE) were performed at room temperature. From the Raman spectra recorded from InN films under hydrostatic pressure up to 13 GPa, linear pressure coefficients and the corresponding Gruneisen parameters for both E-2 and A(1) (LO) phonons were extracted for the wurtzite structure up to 11 GPa, close to the starting pressure of the hexagonal to rock-salt phase transition of InN. Spectra at higher pressure suggest that InN undergoes a gradual phase transition, and the reverse transition exhibits a strong hysteresis effect during the downstroke. Then, we discuss recent results on large single InN islands grown on GaN buffer layers, obtained by spatially resolved micro-Raman measurements. The magnitude of the residual strain is estimated, using a recent determination of phonon deformation potentials. It is found to vary linearly as a function of island height.