Observation of LO-phonon localization in GaAs quantum wires on faceted (311)A surfaces

The localization of longitudinal optical phonons in GaAs/AlAs lateral superlattices and quantum wires grown on faceted GaAs (311)A surfaces are investigated by means of Raman scattering spectroscopy. The frequencies of the localized phonons are found to decrease as the average thickness of the GaAs layer is decreased from 21 to 15 Å. As the GaAs thickness is decreased further to 11.3 and 8.5 Å, the frequencies of the localized phonons increases sharply in connection with the formation of an array of quantum wires. The frequencies calculated in a two-dimensional chain model agree with the experimental values. This makes it possible to interpret the increase in the frequencies of localized phonon states as being the result of the quantization of phonons in the array of one-dimensional objects. The results obtained support the model of GaAs (311)A surface faceting with a facet height of 10.2 Å. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 942–946 (25 June 1996)