Scaling nanowire-supported GaN quantum dots to the sub-10-nm limit, yielding complete suppression of the giant built-in potential

TL;DR

This paper presents a novel single-step epitaxial growth technique to create ultra-scaled GaN nanowire quantum dots, achieving strong quantum confinement and nearly complete suppression of built-in electric fields, advancing UV photonics and single-photon sources.

Contribution

A new simple growth method enables reduction of GaN nanowire quantum dots to sub-10 nm size with suppressed electric fields, enhancing their optical properties.

Findings

Quantum dot diameter reduced to sub-10 nm

Built-in electric fields nearly eliminated

Potential for high-efficiency UV emitters

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 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.