From Raman scattering on a-plane wurtzite ZnO crystals we obtained a decreasing splitting between longitudinal and transversal optical phonons with A1 and E1 symmetry as a function of hydrostatic pressure up to 5.5 GPa. Consequently, the transverse effective charge (e*T) exhibits a strong reduction with increasing pressure, yielding 2.17-14.6× 10-3 P/GPa and 2.04-13.7× 10-3 P/GPa (in units of the elementary charge) for the A1 and E1 phonons, respectively. We find a clear systematic in the linear pressure coefficient of e*T with bond polarity for the series of wide-band gap semiconductors SiC, AlN, GaN, and ZnO. © 2010 American Institute of Physics.
|Journal||Applied Physics Letters|
|Publication status||Published - 18 Jun 2010|