Piezoelectric lattice vibrations in GaN at optical frequencies

At optical frequency range, lattice vibrations in piezoelectric crystal are associated with ionic polarizations. A relationship is formulated, based on classical dispersion theory, involving the dielectric constant (εjj) and the piezoelectric coefficient (djj) of wurtzite GaN. The relation is utilized to investigate the piezoelectric lattice vibrations in GaN at optical frequency, and a close agreement between the computed and the experimental value of djj is found. The study reveals that applications of piezoelectric nature of GaN could be extended to optical frequencies to generate phase coherent acoustic phonons to modulate thermal conduction. At optical frequencies there are no direct experimental methods exist at present for measurement of djj; however, the proposed relation can help to determine djj from infrared reflection measurements.