Confinement of phonons in InGaAs/InP superlattices

A comparison is presented of optical mode Raman spectra of an In0.48Ga0.52A s/InP superlattice, an In0.48Ga0.52As strained epilayer on InP, and bulk In P. The sharpness of the interfaces between the alloy and InP layers in the superlattice sample is confirmed through the observation of folded acoustic modes up to folding index m = 6. Mixed interface modes were correspondingl y not observed in the superlattice optic mode Raman spectra. The GaAs-like longitudinal optic (LO) and transverse optic and InP LO modes in the superl attice are found to decrease in frequency with respect to the corresponding strained-epilayer and bulk-InP modes. These frequency shifts arise from ph onon confinement effects in the superlattice. (C) 2000 American Institute o f Physics. [S0003-6951(00)03528-2].