Phonon Raman scattering in quantum wires

Phonons in narrow quantum wires of In0.53Ga0.47As showing strong one-dimensional confinement of carriers have been studied by Raman spectroscopy. A strong enhancement of the Raman intensity of the longitudinal optical phonon of the wires is observed for wire widths decreasing down to 40 nm. For narrower wires (10-30 nm), the Raman intensity falls very rapidly as the surface roughness becomes comparable to the wire width. No changes in the phonon frequency have been observed. The increased Raman intensity is attributed to enhanced resonance effects due to the one-dimensional confinement of carriers. The role of wavevector non-conservation and surface electric fields on the Frohlich scattering efficiency are discussed.