Formation of misfit dislocations and stacking faults in high indium content In_xGa_1-xN layers grown by metalorganic chemical vapor deposition

We have investigated the relaxation of the misfit strain by the formation of misfit dislocations and stacking faults in high indium (In) content In_xGa_1-xN layers grown by metal-organic chemical vapor deposition (MOCVD). The misfit dislocations in the highly mismatched In_0.33Ga_0.66N/GaN system are generated not only at the InGaN/GaN interface but also within an In_0.33Ga_0.66N layer. It indicates that the InGaN layer in the interface is partially relaxed and the considerable residual strain is relaxed within the In_0.33Ga_0.66N layer. In addition, we observed that stacking faults play the role of a seed in the formation of misfit dislocations within a high In content In_xGa_1-xN layer. For the high In content In_xGa_1-xN layer grown on the thick GaN layer, misfit strain is relaxed by the formation of misfit dislocations and the random stacking faults. For the high In content In_xGa_1-xN layer grown on sapphire substrate with a thin buffer layer, a higher residual strain than GaN/sapphire is found, which is relaxed by the formation of the periodic stacking faults in the InGaN layer.