Macroscopic Polarization Effect on Bowing Constant of Thermal Parameters of InxGa1−xN

Abstract

In this work, we have investigated theoretically the effect of macroscopic polarization [sum of spontaneous (SP) and piezoelectric (PZ) polarization] on various physical parameters of InxGa1−xN alloy. The macroscopic polarization contributes to the effective elastic constants of InxGa1−xN alloy. This modifies the phonon group velocity, Debye temperature, and Debye frequency of the alloy. These thermal parameters are estimated as a function of In composition. Our calculation shows that these material parameters are enhanced and vary nonlinearly with In composition, i.e., show bowing. The cause of bowing is the nonlinear dependence of the spontaneous and piezoelectric polarization on composition. The bowing constant of each material parameter (with and without polarization) is also theoretically predicted by the best-fit method. The results show that the polarization mechanism not only enhances the parameters but also contributes significantly to the bowing constant. The macroscopic polarization contributes more than 25% to the bowing constant. The obtained results can be used to predict the effect of the polarization mechanism on the thermoelectric properties of InxGa1−xN alloy.