Micro-Raman spectroscopy of a single freestanding GaN nanorod grown by molecular beam epitaxy

Micro-Raman spectra were measured on a single freestanding GaN nanorod, which was grown by molecular beam epitaxy. A sharp linewidth of E2 (high) mode of 2.1 cm-1 measured in the x (y,y) x- configuration indicates the high crystalline quality of the nanorod. The angle-dependent Raman spectroscopy shows that the integrated intensities of these first-order Raman modes follow the theoretical sinusoidal functions. The forbidden E1 (LO) mode that appeared in the x (z,z) x- scattering configurations is assigned to the quasi-LO phonon mode. Power-dependent Raman spectroscopy shows redshift with increasing laser power density due to sample heating which is confirmed by Stokes and anti-Stokes measurements. The broadband centered at 708.5 cm-1 is ascribed to the surface mode of the nanostructure.