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Metal-organic chemical vapor deposition was successfully used to grow un-doped nonpolar a- plane AlGaN on an r- plane sapphire substrate. High-resolution x-ray (HR-XRD), atomic force microscopy, Polarization Indirect Microscopic Imaging, and Hall effect measurement were used to investigate the effect of the nonpolar a- plane AlGaN layer on the graded AlGaN buffer layer. The results reveal that inserting the AlGaN-graded layer improves the crystalline quality and morphology of the surface. The root means the square value was less than 1.47 nm, while the background electron concentration was $-3.9\times {10}^{17}\,{{\rm{cm}}}^{-3}.$ In addition, the HR-XRD full width at half maximum indicates improved crystalline quality.