Selective area growth of high quality GaN nanocolumns on Si(0 0 1) by plasma assisted molecular beam epitaxy

Two different arrays of GaN nanocolumns, with average diameters of 140 nm and 260 nm, were selectively grown by molecular beam epitaxy on GaN-buffered on-axis Si(001) substrates. Footprint of the nanocolumns with respect to the grain size of the GaN buffer layer plays and important role on the crystalline quality of the nanocolumnar material. Despite the rather low crystalline quality of the GaN buffer, very high quality GaN nanocolumns were achieved in the case of the array with 140 nm average diameter, as indicated from a low temperature photoluminescence donor-bound exciton linewidth of 1.9 meV and negligible densities of stacking faults and threading dislocations determined by transmission electron microscopy. These results may help to the integration of GaN-based nano-devices with the conventional Si(001) electronics platform.