Study of the Raman spectra of phonons in disordered GaSb/AlSb (001) superlattices

摘要

In the present work, we study the influence of disorder in the Raman spectra of the phonons of (GaSb)(n)/(AlSb)(n) (001) superlattices (SLs), for n = 1, 2. The disordered superlattices are approximated with primitive cells that are much larger than the primitive cells of the corresponding perfect SLs. We propose that disorder appears because of deviations from the sequence of the GaSb and AlSb layers, which is imposed by symmetry, or because of intermixing of Ga and Al in the cation lattice planes. The dynamical matrix of each SL is constructed from the combination of the dynamical matrices of the bulk crystalline constituents, which have been calculated at certain points of the Brillouin zone with a ten-parameter valence overlap shell model. Further, we have calculated the Raman spectra of the disordered 1 x 1 and 2 x 2 superlattices grown along the (001) direction, using an eight-parameter bond polarizability model, away from resonance conditions. Our results show that intermixing of Ga and Al cations produce Raman activity that is not present in the phonon spectra of perfect superlattices.