Macroscopic polarization and bowing constant of AlxGa1−xN

In this work, we have theoretically investigated the effect of macroscopic polarization (sum of spontaneous and piezoelectric polarization) on various thermal parameters of AlxGa1−xN alloy. The macroscopic polarization contributes to the effective elastic constant of AlxGa1−xN alloy. This contribution modifies the phonon group velocity, Debye temperature and Debye frequency of the alloy. The revised values of these thermal parameters have been estimated as a function of Al composition. Our calculation shows that these thermal parameters are enhanced and vary non-linearly with Al composition i.e., they show bowing. The cause of this bowing is the non linear dependence of spontaneous and piezoelectric polarization on Al composition. The bowing constant of above thermal parameters (with and without polarization) has been theoretically predicted by method of best fit. The results show that polarization mechanism not only enhances the parameters but also contribute significantly to bowing constant. The macroscopic polarization contributes around 48% to bowing constant of above thermal parameters. The obtained result will be useful for simulation of nitride optoelectronics devices to predict the effect of polarization mechanism on thermoelectric properties of AlxGa1−xN alloy.