Dispersive Spectra of Phonon Modes and Fröhlich Electron–Phonon Coupling Properties in AlGaN Quantum Rings: Wurzite versus Zinc‐Blende Structure

Abstract

The influence of crystal structure on the phonon modes and electron–phonon coupling properties in nitride quantum ring (QR) structures is investigated based on the macroscopic dielectric continuum model. It is found that three types of phonon modes including the surface optical (SO) phonon modes, the exact confined (EC) modes, and quasiconfined (QC) modes can coexist in the wurtzite nitride QR. However, only the SO modes and EC modes may appear in zinc‐blende nitride QR, and the QC modes cannot exist in zinc‐blende QRs in general. Numerical calculation on AlN QR shows that the SO modes of zinc‐blende QR are more dispersive than those of wurtzite QR. Furthermore, the degenerative behavior of QC modes to SO modes in wurtzite QRs is clearly observed. Moreover, the electron–phonon coupling functions in zinc‐blende QRs are larger than those in wurtzite QRs. These results reveal that the crystal structures greatly affect not only the type of phonon mode, but also the coupling strength of electron–phonon interaction. The present theoretical scheme and the numerical results are quite useful and important for further understanding and investigating the polaronic effect and related physical properties in wurtzite and zinc‐blende nitride QRs.