Crystal-phase quantum dots in GaN quantum wires
  We study the nature of excitons bound to I1 basal plane stacking faults in ensembles of ultrathin GaN nanowires by continuous-wave and time-resolved photoluminescence spectroscopy. These ultrathin nanowires, obtained by the thermal decomposition of spontaneously formed GaN nanowire ensembles, are tapered and have tip diameters down to 6 nm. With decreasing nanowire diameter, we observe a strong blue shift of the transition originating from the radiative decay of stacking fault-bound excitons. Moreover, the radiative lifetime of this transition in the ultrathin nanowires is independent of temperature up to 60 K and significantly longer than that of the corresponding transition in as-grown nanowires. These findings reveal a zero-dimensional character of the confined exciton state and thus demonstrate that I1 stacking faults in ultrathin nanowires act as genuine quantum dots. 
P. Corfdir, C. Hauswald, O. Marquardt, T. Flissikowski, J. K. Zettler,   S. Fern\'andez-Garrido, L. Geelhaar, H. T. Grahn, a...
cond-mat.mes-hall