Acoustic waves in (0001) III-N and MgO/ZnO superlattices

We study the acoustic waves of (0001) wurtzite MgO-ZnO and III-N superlattices. We obtain the dispersion curves as a function of the wavevector parallel to the interfaces. We consider different ranges of the thicknesses of the constituent materials forming the superlattices. Due to the transverse elastic isotropy of the basal plane of the wurtzite structure there is a decoupling of the transverse waves propagating in this plane from the coupled displacements of the sagittal waves. The dispersion curves show a qualitative picture similar in all the superlattices considered here for each of the thickness ranges studied. The sagittal waves show important differences in the dispersion curves when compared with the transverse waves. They show gaps of irregular shape not present in the transverse wave dispersion curves.