Resonant raman scattering in hexagonal GaN

We performed resonant Raman scattering in hexagonal GaN using discrete laser lines in the violet and UV spectral range for optical excitation. To tune the energetic position of the fundamental gap E(ind 0) of GaN relative to the exciting photon energy the sample temperature was varied between 77 and 870 K. Analyzing both Stokes and anti-Stokes Raman spectra, the resonance profiles for Fröhlich-induced one-E(ind 1)(L0) and two-E(ind 1)(L0) phonon scattering could be deduced, covering the energy range from 0.5 eV below the E(ind 0) gap up to the gap energy. The strength of deformation-potential scattering by the A(ind1)(T0) mode was used as an internal reference. For excitation slightly above the E(ind 0) gap energy E(ind 1)(L0) multiphonon scattering up to the fourth order was observed, which reflects the stronger polarity of the Ga-N bond as corn~ to conventional III-V semiconductors.