Comparative study on hydrostatic strain, stress and dislocation density of Al_0.3Ga_0.7N/GaN heterostructure before and after a-Si₃N₄ passivation

The hydrostatic strain, stress and dislocation densities were comparatively analyzed before and after passivation of amorphous silicon nitride (a-Si₃N₄) layer on Al_0.3Ga_0.7N/GaN heterostructure by nondestructive high resolution x-ray diffraction (HRXRD) technique. The crystalline quality, in-plane and out-of plane strain were evaluated from triple-axis (TA) (ω-2θ) diffraction profile across the (002) reflection plane and double-axis (DA) (ω-2θ) glancing incidence (GI) diffraction profile across (105) reflection plane. The hydrostatic strain and stress of Al_0.3Ga_0.7N barrier layer were increased significantly after passivation and both are tensile in nature. The dislocation density of GaN was also analyzed and no significant change was observed after passivation of the heterostructure. The crystalline quality was not degraded after passivation on the heterostructure confirmed by the full-width-half-maximum (FWHM) analysis