Raman spectroscopy has proven to be an informative and nondestructive technique in characterization of nanostructures including local chemical and strain analysis. In this paper the confocal Raman microscopy have been used for the high-spatial-resolution characterization of phonon excitations in AlGaN/GaN heterostructures. These heterostructures were grown on Al₂O₃(0001) substrate with thickness 3 mm and 450 μm. The influence of the crystal inhomogeneous  induced by strain, mosaic structure and dislocationson, on the phonon spectra of nitride layers, were studied. Stress values were obtained from the frequency shift of the E₂ (Al)GaN phonon. The measured micro-Raman results have shown the clear gradient distributions of strain along the heterostructure growth direction  within both the wurtzite AlGaN/GaN layers and interface layers of the sapphire substrate. It is shown that considerable divergence in the deformation constant data in the literature,  concerning of nitride heterostructures, are cased by the mosaic crystal structure peculiarities  of nitride layers. Therefore, to characterize the local deformation states at nano-scale of the A³N heterostructures, the combined micro-Raman microscopy together with high-resolution X-ray diffraction technique should be used. It enable us to calculate the exact value of the phonon deformation potential.

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