Room-temperature photoluminescence and resonance-enhanced Raman scattering in highly degenerate InN films

Abstract

We report the results of room-temperature photoluminescence (PL) and resonance-enhanced Raman scattering studies on highly degenerate (carrier concentration >3×1020cm−3) InN films grown on c-plane sapphire substrates by plasma source molecular-beam epitaxy. Carrier concentration-dependent PL emission peak is observed in the 1.4–1.8 eV range. These films show strong resonance-enhanced first- and second-order Raman scattering under 785 nm (1.58 eV) excitation energy and not with 514.5 nm (2.41 eV) excitation, suggesting the existence of electronic states ∼1.5eV in these samples. The PL emission peak energies and their dependence on the carrier concentration are consistent with the observed optical absorption edges. These results are compared to the data on single crystalline, low degenerate InN film grown by molecular-beam epitaxy, which shows a band-gap energy of ∼0.6eV. The results imply a large shift in the optical absorption edges due to band filling effects in the highly degenerate InN samples.