Stacked structure of self-organized cubic InN nano-dots grown by molecular beam epitaxy



A two-stacked cubic (c-) InN/c-GaN nano-scale dot structure is fabricated on a MgO(001) substrate by RF-N2 molecular beam epitaxy and its microstructures are investigated by scanning transmission electron microscopy (STEM). The cubic lattice structure of InN dots is verified by STEM observations. It is implied that c-InN dots formed on a smooth c-GaN surface have the {111} facets. The c-GaN cap layer has an uneven surface, which reflects the shape of the c-InN dots embedded beneath the cap layer. InN selectively deposits in concave regions on the c-GaN cap layer, which appear above in-between positions of embedded dots. Thus, stacked c-InN/c-GaN dots do not tend to align vertically. These results open the possibility for multi-stacking structures of c-InN dots and their application to high-performance optoelectronic devices based on the nitride semiconductors. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)