Intermediate-coupling poltarons in GaN, AlN, and InN

A variational approach is adopted to study the intermediate-coupling polaron for bulk III-V nitride semiconductors with wurtzite crystalline structure in the long-wavelength limit based on the macroscopic dielectric continuum model and the uniaxial model. The polaronic self-trapping energy and effective mass are analytically derived for the LO and TO polarization mixing due to the anisotropic effect. The numerical computation has been performed to obtain the polaronic self-trapping energy and effective mass for wurtzite nitrides GaN, AlN, and InN. The results show that the self-trapping energies of the wurtzite nitrides are bigger than the zinc-blende structures for the calculated materials. It is also found that the structure anisotropy increases the electron-phonon interaction in wurtizte nitride semiconductors. It indicates that the LO-like phonon influence on the polaronic effective mass and self-trapping energy are dominant, and the anistropic effect is obvious.