Resonant Raman scattering in self-assembled GaN/AlN quantum dots

Self-assembled GaN/AlN quantum dots have been investigated by means of Raman scattering. A resonant enhancement of the Raman peaks has been observed when the excitation is tuned above the GaN band-gap energy. The polar mode nature, either quasiconfined or interfacial, has been assigned after comparing with the polar optical modes of spheroidal dots calculated within the framework of the anisotropic dielectric continuum model. The built-in strain of the GaN dots induced a substantial blueshift of the nonpolar E-2H Raman mode frequency. A theoretical model that analyzes the three-dimensional strain distribution in the quantum dots has been employed for estimating the strain contribution to the frequency shifts of both nonpolar and polar optical modes.