Interface-phonon–electron interaction potentials and dispersion relations in III-nitride-based structures

In dimensionally confined multilayer heterostructures, phonons that are joint modes of the materials composed of these heterostructures are known to exist over specific frequency ranges. These modes, known as interface phonons, can exhibit phonon-electron interactions that are enhanced as the thicknesses of the layers of the heterostructure are reduced in size to about 10 nm or less. These modes have been shown to be important in phonon engineering and have been applied in optoelectronic and electronic devices, primarily for semiconductor heterostructures with underlying cubic lattices, with few studies existing for heterostructures based on wurtzite III-nitride. Motivated by applications of interface modes in ternary-based nitride structures, such as heat transport, this paper presents generalized expressions for the phonon-electron Frohlich interactions as well as the dispersion relations for these joint modes for the technologically important case of III-nitride materials. Frequency conditions are found to restrict the existence of interface modes as illustrated through several structures.