Effects of disorder on the Raman spectra of GaAs/AlAs superlattices

The vibrational properties of GaAs/AlAs (001) superlattices are studied theoretically by means of an ab initio approach-based on interatomic force constants-that allows one to treat the effects of compositional disorder using very large supercells. We find that the experimental Raman spectra in thin samples cannot be explained without taking into account disorder occurring at the interfaces. Moreover, we show that some of the AlAs-like LO modes are extremely sensitive to disorder, and they are therefore suitable for a rather precise characterization of the samples.