Evidence for Phase-Separated Quantum Dots in Cubic InGaN Layers from Resonant Raman Scattering

The emission of light in the blue-green region from cubic ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ alloys grown by molecular beam epitaxy is observed at room temperature and $30\mathrm{K}$. By using selective resonant Raman spectroscopy (RRS) we demonstrate that the emission is due to quantum confinement effects taking place in phase-separated In-rich quantum dots formed in the layers. RRS data show that the In content of the dots fluctuates across the volume of the layers. We find that dot size and alloy fluctuation determine the emission wavelengths.