Effect of Piezoelectric Polarization on Phonon group velocity in Wurtzite Nitrides

TL;DR

This study examines how piezoelectric polarization influences phonon group velocities in wurtzite nitrides, revealing modifications that impact thermal properties and phonon relaxation rates in these materials.

Contribution

It provides a detailed analysis of the effect of piezoelectric polarization on phonon velocities in binary and ternary nitrides, incorporating literature-based piezoelectric tensor values.

Findings

Piezoelectric polarization modifies phonon group velocities.

Percent change in velocities depends on piezoelectric tensor values.

Ternary nitrides show small positive bowing in phonon velocities.

Abstract

We have investigated the effect of piezoelectric (PZ) polarization property on group velocity of phonons in binary as well as in ternary wurtzite nitrides. It is found that with the presence of PZ polarization property, the phonon group velocity is modified. The change in phonon group velocity due to PZ polarization effect directly depends on piezoelectric tensor value. Using different piezoelectric tensor values recommended by different workers in the literature, percent change in group velocities of phonons has been estimated. The Debye temperatures and frequencies of binary nitrides GaN, AlN and InN are also calculated using the modified group velocities. For ternary nitrides AlxGa(1-x)N, InxGa(1-x)N and InxAl(1-x)N, the phonon group velocities have been calculated as a functions of composition. A small positive bowing is observed in phonon group velocities of ternary alloys. Percent variations in phonon group velocities are also calculated for a straightforward comparison among ternary nitrides. The results are expected to show a change in phonon relaxation rates and thermal conductivity of III-nitrides when piezoelectric polarization property is taken into account.