Scaling Nanowire-Supported GaN Quantum Dots to the Sub-10 nm Limit, Yielding Complete Suppression of the Giant Built-in Potential

Abstract

The nanowire-supported quantum dot (NWQD) of GaN is an unconventional nanostructure, which is extremely promising for realization of UV photonics in general and roomtemperature 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 ultrascaled 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.