  A pencil-like morphology of homoepitaxially grown GaN nanowires is exploited
for the fabrication of thin conformal intrawire InGaN nanoshells which host
quantum dots in nonpolar, semipolar and polar crystal regions. All three
quantum dot types exhibit single photon emission with narrow emission line
widths and high degrees of linear optical polarization. The host crystal region
strongly affects both single photon wavelength and emission lifetime, reaching
subnanosecond time scales for the non- and semipolar quantum dots. Localization
sites in the InGaN potential landscape, most likely induced by indium
fluctuations across the InGaN nanoshell, are identified as the driving
mechanism for the single photon emission. The hereby reported pencil-like InGaN
nanoshell is the first single nanostructure able to host all three types of
single photon sources and is, thus, a promising building block for tunable
quantum light devices integrated into future photonic circuits.
