Photoexcited carriers and surface recombination velocity in InN epilayers: A Raman scattering study

The effect of photoexcited electron-hole pairs on the LO-phonon-plasmon coupled modes has been observed in InN layers by means of micro-Raman experiments performed at different excitation laser powers. The L-Raman peak displays an upward shift of about 10 cm(-1) over the range of increasing excitation powers studied. The L-behavior is well accounted for by a dielectric line-shape model based on the Lindhard-Mermin dielectric function. The photoexcited carrier density has been extracted from line-shape fits to the Raman spectra and a linear increase in the photoexcited carrier density with incident power is found. A simple diffusion model is used to estimate the surface recombination velocity in the layers, which is found to be in the 4.6-4.9 x 10(4) cm s(-1) range for the bare InN surface.