  The piezoelectric (PZ) polarization effect enhances the phonon group velocity
in wurtzite nitrides. This enhancement influences the phonon relaxation rates.
We calculate the modified phonon relaxation rates in binary wurtzite nitrides
(GaN, AlN and InN) by considering process like umklapp process, point defect,
dislocation, boundary and phonon-electron scattering. The result will be useful
to study the effect of PZ polarization on thermal conductivity of binary
wurtzite nitrides (GaN, AlN and InN).
