Lattice Vibration of Thin-Layered AlAs-GaAs Superlattices

This paper presents a theoretical investigation into the Raman spectra of the (AlAs) 1 (GaAs) 1 and (AlAs) 2 (GaAs) 2 superlattices using the normal coordinate treatment based on a rigid-ion model. The model involves a three-dimensional crystal lattice, long-range Coulomb interaction due to atomic ionicity, and the short-range interactions between neighbor atoms farther out. The results are compared with the observed Raman spectra of the (AlAs) 1 (GaAs) 1 and (AlAs) 2 (GaAs) 2 superlattices grown by flow-rate modulation epitaxy. Considering the interactions between the first, second and third nearest neighbors to be the short-range interactions, the experimental results are well reproduced by the theoretical calculations. Effective interactions are confirmed to exist between the Al and Ga atoms in the second nearest neighbors, and the Ga and As atoms in the third nearest neighbors.