Raman scattering characterization of interface broadening in GaAs/AlAs short period superlattices grown by molecular beam epitaxy

We analyze in this letter the Raman scattering spectra on several GaAs/AlAs short period superlattices grown by molecular beam epitaxy with different substrate temperatures and different doping concentrations. The frequency and Raman intensity of both folded acoustical and confined optical phonons, which are observed in all samples, are clearly related to the substrate temperature. These variations: (i) decreasing intensity of the folded acoustical modes, (ii) frequency shift of the optical modes confined in GaAs, are successfully analyzed in terms of interface broadening. A quantitative estimation of the interface widths is obtained and analyzed.