Résumé
Raman spectroscopy is used to study the effect of the built-in biaxial stress on the E2 and A1 (LO) q=0 phonon modes of wurtzite GaN layers deposited by metal organic vapor phase epitaxy on (0001) sapphire substrate. By means of phonon frequency shifts, the biaxial pressure coefficients of the mode frequencies are determined and used to calculate the corresponding deformation potentials. Stress calibration has been performed using reflectance data.