Phonon deformation potentials of the E₂(high) phonon mode of Al_xGa_1-xN

Micro-Raman spectroscopy was applied to study the E-2(high) phonon deformation potentials in AlxGa1-xN material, which are required to convert phonon frequency shifts into stress values. AlxGa1-xN layers were grown by molecular beam epitaxy directly on (111)-oriented Si substrates. Mechanical bending was applied to introduce biaxial stress in the AlxGa1-xN layers and Raman shifts were measured as a function of the applied deformation. The Si phonon mode provided a reference for the applied stress and allowed determination of phonon deformation potential values for AlxGa1-xN. Deformation potentials of the GaN- and AlN-like E-2(high) phonon mode of AlGaN alloys were found to be similar to the corresponding values of binary compounds.