Theoretical calculation of the vibrational and thermal properties of wurtzite InN-GaN multiple quantum well superlattice

Abstract

In this study, the phonon dispersion of a wurtzite InN-GaN multiple quantum well superlattice was produced using a modified adiabatic bond charge model. Bulk binary compound parameters obtained from ab initio calculations were used as input parameters for the modified bond charge model. The phononic bandgap, visualization of the vibrational modes, specific heat, and thermal conductivity in the quantum confined direction for the superlattice material are reported. The size of the phononic bandgap is predicted to be between that of the two bulk materials in all symmetry directions and insufficient to prevent first order phonon decay. Surprisingly, the A1-like mode has a greater vibration frequency than the E1-like mode, which is opposite to what was believed in the bulk counterparts. The specific heat of the superlattice is similar to that of GaN, despite similar volumetric fractions of the materials. The low thermal conductivity of InN limits the thermal conduction in the confined direction.