Picosecond time-resolved Raman studies of confined and interface optical phonons in short-period GaAs-AlAs multiple quantum well structures

Picosecond time-resolved Raman spectroscopy was used to measure the population relaxation time of various confined and interface optical phonon modes in a series of short-period GaAs-AlAs multiple quantum well structures. The results demonstrate that within the experimental accuracy, the lifetime of various confined and interface optical phonon modes in the GaAs layers does not depend upon the GaAs well width. This is in good agreement with recent calculations by Gupta and Ridley in which optical phonons were assumed to decay into bulk-like acoustical phonons. The results also suggest that the light-scattering mechanism in this experiment is the defect-induced Fröhlich mechanism.