Selective-area catalyst-free MBE growth of GaN nanowires using a patterned oxidelayer

Abstract

GaN nanowires (NWs) were grown selectively in holes of a patterned silicon oxide mask, byrf-plasma-assisted molecular beam epitaxy (PAMBE), without any metal catalyst. Theoxide was deposited on a thin AlN buffer layer previously grown on a Si(111) substrate.Regular arrays of holes in the oxide layer were obtained using standard e-beam lithography.The selectivity of growth has been studied varying the substrate temperature, galliumbeam equivalent pressure and patterning layout. Adjusting the growth parameters, GaNNWs can be selectively grown in the holes of the patterned oxide with completesuppression of the parasitic growth in between the holes. The occupation probability of ahole with a single or multiple NWs depends strongly on its diameter. The selectively grownGaN NWs have one common crystallographic orientation with respect to theSi(111) substrate via the AlN buffer layer, as proven by x-ray diffraction (XRD)measurements. Based on the experimental data, we present a schematic model ofthe GaN NW formation in which a GaN pedestal is initially grown in the hole.