Polaron properties in ternary group-III nitride mixed crystals

Polaron properties are studied in bulk wurtzite nitride ternary mixed crystals AxB1-xN (A, B = Al, Ga, In) with the use of a dielectric continuum Fröhlich-like electron-phonon interaction Hamiltonian. The polaronic self-trapping energy and effective mass are analytically derived by taking the mixing properties of the LO and TO polarizations due to the anisotropy effect into account in the mono-phonon approximation. The numerical computation has been performed for the wurtzite ternary mixed crystal materials InxGa1-xN, AlxGa1-xN, and AlxIn1-xN as functions of the composition x. The results show that the polaronic self-trapping energies in the wurtzite structures are bigger than that in zinc-blende structures for the materials calculated. It is also found that the structure anisotropy increases the electron-phonon interaction in wurtizte nitride semiconductors. The results indicate that the LO-like phonon influence on the polaronic self-trapping energy and effective mass is dominant, and the anisotropy effect is obvious.