Confined phonons in (GaAs)n1(AlAs)n2 superlattices grown along the [012] direction

The short-period (GaAs)n1(AlAs)n2 superlattices with parameters (n1,n2)=(21,25), (6,42), (14,16), and (23,8) have been grown by molecular beam epitaxy on GaAs substrates along the [012] direction and characterized by x-ray and Raman scattering spectroscopy. The appearance of distinct satellite peaks around the Bragg reflections demonstrates the formation of high quality superlattices. The observed TO and LO confined modes have frequencies which map closely those of the optical phonons of bulk GaAs and AlAs in the Γ-W-X direction.