In order to examine the effect of threading dislocations on the structure of InGaN/GaN multiple quantum wells grown by metal-organic vapour-phase epitaxy, epitaxial lateral overgrowth on a patterned sapphire substrate was employed and the multiple quantum wells were characterized as a function of the lateral position in terms of cathode luminescence, transmission electron microscopy and scanning transmission electron microscopy. The intensity of a blue luminescence peak (426nm) was larger for the epitaxial layer overriding on the masks than that for the layer on the unmasked area, while the peak wavelength was independent of the position. Threading dislocations, which were generated at the GaN/sapphire interface, did not propagate to the surface of GaN layer on the masks. The thicknesses of both the InGaN well and the GaN barrier, on the other hand, were the same for the multiple quantum wells both on the unmasked surface and on the masks, which was consistent with the invariable peak wavelength of the blue luminescence. For an InGaN well with the indium content of around 10%, it seemed that the existence of threading dislocations does not affect the structure of the multiple quantum wells but just reduces the luminescence intensity through a recombination via mid-gap states.

Optical and Structural Characterization of InGaN/GaN Multiple Quantum Wells by Epitaxial Lateral Overgrowth. M.Sugiyama, T.Shioda, Y.Tomita, T.Yamamoto, Y.Ikuhara, Y.Nakano: Materials Transactions, 2009, 50[5], 1085-90