Résumé
The photoluminescence and Raman spectra of several Ga 1−x Al x N layers (0 ≤ x ≤ 0.86) grown on sapphire substrates by metal-organic vapor phase epitaxy have been recorded at room temperature, under an excitation at 244 nm. Using the photoluminescence spectra, the variation of the band gap of these alloys can be followed only up to x = 0.5. From resonant Raman scattering, it can be deduced that the band gap energy of the solid solution for x very close to 0.7 corresponds to the incident photon energy (5.08 eV). This result is confirmed by a detailed comparison of the present work with previous experimental data on the A 1 (LO) phonon peak position, obtained under visible excitation.