Microstructural Characterization of V-Defects in InGaN/GaN Multiquantum Wells

InGaN multiple-quantum-well (MQW) structures grown by metal-organic chemical-vapor deposition (MOCVD) are found to contain V-defects attached to threading dislocations. The nature of the V-defects was evaluated using transmission electron microscopy (TEM), atomic force microscopy (AFM), and secondary ion mass spectroscopy (SIMS). Some (a + c) dislocations were shown to decompose inside the multi-quantum well, giving rise to a misfit segment in the c-plane and a V-defect. The V-defects in the multiple-quantum- well have the thin six-walled structure with InGaN/GaN{10 (1) over bar1} layers. The mechanism of formation of these defects has been discussed in terms of stress induced by lattice mismatch and reduced In incorporation on the {10 (1) over bar1}planes in comparison to the (0001) surface.