Microstructure and dislocation evolution in composition gradient AlGaN grown by MOCVD

Abstract In this study, the epitaxial growth of the full-composition-graded AlxGa1-xN films has been demonstrated on the sapphire substrates by using metalorganic chemical vapor deposition (MOCVD). The aluminum composition in the AlxGa1-xN films has been precisely controlled from 0 to 100%, as confirmed by X-ray diffraction and energy-dispersive spectroscopy analyses. The pseudo-periodic AlxGa1-xN/AlyGa1-yN structures are spontaneously formed during the initial growth of the graded AlGaN layer, which facilitate the strain relaxation. In addition, the behavior of the bending dislocations has been investigated in detail, and the threading dislocation bending along the growth direction is noted to relax the strain further.