Anisotropy effects on polar optical phonons in wurtzite GaN/AlN superlattices

Polar optical phonon states and their dispersive spectra of a wurtzite nitride superlattice with complex bases: Transfer-matrix method

“…The numerical result reveals that there are five types of phonon modes in the wurtzite GaN/Al x Ga 1−x N/Al y Ga 1−y N three-layer SLs chosen here. The dispersive spectra behave as a series of frequency bands, which are narrower than those in wurtzite two-layer GaN-based SLs [20,34,35]. The present theoretical scheme and numerical results are important and useful for further experimental and theoretical investigations of the polar phonon modes behaviors and their effect on optoelectronic properties in wurtzite nitride SLs with complex bases.…”

“…In order to get a clear picture for the dispersive behaviors of the types of polar optical phonon modes in wurtzite complex bases SL systems, an application of the present theories based on a nitride SL with GaN/Al 0.15 Ga 0.85 N/AlN three-layer complex bases is performed, and a numerical calculation of dispersive relationship is carried out. The material parameters used in our calculations are listed in table 1 [26,27,34]. Table 1.…”

“…Taking into account the oscillating or decaying waves in n-layers of some unit cell in the complex bases SL structures, it can be confirmed that 2 n types of polar phonon modes are likely to exist in wurtzite GaN-based SLs with n-layer complex bases. They are the IO phonon mode (ζ i (ω) > 0), the PR phonon mode (ζ i (ω) < 0) [25,34], and the (2 n − 2) types of the QC phonon modes (at least one ζ i (ω) > 0, and one ζ j (ω) < 0, i = j) [34,37,39] in wurtzite SLs, respectively. These QC modes are distinguished and labeled as follows.…”

“…On the basis of the dielectric continuum approximation and Loudon's uniaxial crystal model [33], several authors have made their great contributions to the study of the polar optical phonons and their electron-phonon interactions in wurtzite nitride binary SLs [20,34,35]. For example, Gleize and his coworkers [34] investigated the anisotropy effects on polar phonon modes in wurtzite GaN/AlN SLs, and the quasi-confined (QC) phonon modes and interface-optical (IO) phonon modes were found in the SL structures.…”

“…For example, Gleize and his coworkers [34] investigated the anisotropy effects on polar phonon modes in wurtzite GaN/AlN SLs, and the quasi-confined (QC) phonon modes and interface-optical (IO) phonon modes were found in the SL structures. Medeiros, Anselmo and their cooperators studied the confinement of polar optical phonons in two-layer periodic GaN/AlN SLs [35] based on the dielectric continuum model (DCM), and the phonon dispersive spectra of the systems were displayed in their discussions.…”