Dispersion relations of interface and quasi-confined phonon modes in ZnO/BeZnO quantum wells

Abstract

The long-wave optical phonon frequencies of BexZn1−xO alloys are determined within the modified random-element isodisplacement model. The results indicate a two-mode behavior for A1 and E1 branches of the optical phonons. The dispersions of the interface and quasi-confined modes in the polar ZnO/BexZn1−xO quantum wells are calculated within the dielectric continuum model up to x=0.2. In the absence of strain, the quantum wells yield as many as three distinct frequency ranges for the IF modes. However, the quasi-confined modes have two separate frequency ranges with boundaries determined by the ZnO-like and ZnO phonons. With the inclusion of strain, the boundaries of the frequency ranges for each mode are modified but without any change in the overall picture.