  The nanowire-supported quantum dot (NWQD) of GaN is an unconventional
nanostructure, which is extremely promising for realization of UV photonics in
general, and room-temperature single photon generation, in particular. While
GaN-NWQDs have several promising attributes, the crucial challenge in
exploiting their full potential, is to reduce the lateral dimensions of the
QDs, to the order of the exciton Bohr-radius in GaN. Also critical is to
suppress the built-in electric field due to spontaneous and piezoelectric
polarization, which adversely affects the radiative recombination lifetime. We
report here the innovation of a simple yet powerful single-step epitaxial
growth technique, to achieve both of these targets. By combining controlled and
on-demand thermal decomposition of GaN nanowires, with our previously-developed
strategy of inhibiting the same via AlN-capping, we demonstrate that the
NWQD-diameter can indeed be reduced to the truly strong-quantum-confinement
limit. In these ultra-scaled GaN QDs, we show that the built-in electric fields
are almost completely suppressed. The NWQD fabrication-strategy developed in
this work may pave the way for fabrication of highly efficient classical and
quantum UV-emitters based on GaN.
