Formation of InGaN quantum dots in regularly arranged GaN nanocolumns grown by rf-plasma-assisted molecular-beam epitaxy

InGaN quantum dots (QDs) were successfully integrated at the apex of each pyramid-topped GaN nanocolumn. Various nanocolumn arrays with different nanocolumn diameters arranged in a triangular lattice were prepared on GaN templates by Ti-mask selective-area growth (SAG) with rf-plasma-assisted molecular-beam epitaxy (rf-MBE). The photoluminescence (PL) emission wavelength from the InGaN QDs shifted from 477 to 516 nm with increasing nanocolumn diameter from 206 to 326 nm. From the Arrhenius plot of PL integrated intensity, the PL internal quantum efficiency (IQE) was evaluated to be 48.4% for the 516-nm-wavelength sample. Threading dislocations at the bottom region of the nanocolumns were bent toward the sidewall and did not propagate to the upper active layer, which contributed to the higher PL efficiency. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim