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 freque ncies of the localized phonons are found to decrease as the average th ickness of the GaAs layer is decreased from 21 to 15 Angstrom. As the GaAs thickness is decreased further to 11.3 and 8.5 Angstrom, the freq uencies 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 ph onons in the array of one-dimensional objects. The results obtained su pport the model of GaAs (311)A surface faceting with a facet height of 10.2 Angstrom. (C) 1996 American Institute of Physics.