Abstract
Phonon spectra of GaAs/AlAs superlattices (SLs) grown on (311)A,B and (001) surfaces were studied using Raman spectroscopy. Thethickness of GaAs layers were varied from 1 to10 monolayers (MLs); the thickness of AlAs barriers were 8 ML in the (311)direction. Different polarization geometries of Raman scatteringwere applied to study LO and TO modes. The splitting of TOx(atoms displace in the direction [011̄] perpendicular to thefacets on the (311)A surface) and TOy (atoms displace inthe [2̄33] direction parallel to the facets) modes wasobserved for (311)A SLs. In the case of (311)B SLs no splitting was observed. The phonon anisotropy of (311)A SLs may beindirect evidence of anisotropic structure of quantum objectsformed on the (311)A GaAs surface. In the Raman spectra of theSL containing GaAs submonolayers (SML) grown on a (2×4) reconstructed (100) surface, Raman peaks corresponding toadditional lateral confinement of LO phonons were observed. Thecalculations of Raman spectra were carried out using theBorn-von-Karman model (taking into account Coulomb interactionin the rigid-ion model) and the Wolkenstein bond polarizabilitymodel. According to the calculations, the interface structure strongly influences the Raman spectra of GaAs/AlAsheterostructures containing GaAs SML.
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