Raman scattering study of BxGa1―xN growth on AlN template substrate

In this study, Raman scattering measurements are reported on the BxGa1–xN layers grown on AlN-on-sapphire templates by MOVPE. The boron content covered the composition range from 0% (pure GaN) to 1.75%. The Raman spectra were recorded at 300 K with a confocal micro-Raman spectrometer in the backscattering geometries. Raman cartography at a lateral resolution of 1 µm was performed to study the spatial variation of the phonon peaks characteristics. The homogeneity of BGaN layers was studied and the phonon modes characteristics are determined as a function of composition, with respect to the laser polarisation. The E2 and A1(LO) modes frequencies are shifted with respect to the pure GaN. The A1(LO) mode behaviour correlates well with the free carriers concentration measured by Hall Effect method, indicating a phonon-plasmon coupling decreasing with increasing boron content in alloy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)