Observation of dielectrically confined excitons in ultrathin GaN nanowires up to room temperature

The realization of semiconductor structures with stable excitons at room temperature is crucial for room temperature optoelectronic applications involving excitons. Quantum confinement has commonly been employed for enhancing excitonic effects in semiconductor heterostructures. Dielectric confinement, which gives rises to much stronger enhancement, has proven to be more difficult to achieve because of the rapid nonradiative interface recombination in hybrid dielectric/semiconductor structures. In this context, GaN nanowires appear to be a suitable platform for optoelectronic applications based on dielectrically enhanced excitons. GaN nanowires form spontaneously on a wide variety of substrates, they are free of threading dislocations, and recombination at the surface of the GaN nanowires is inefficient even in the absence of passivation.

Figure: (Top left) Ultrathin GaN nanowires have been obtained by thermally decomposing GaN nanowires grown by molecular beam epitaxy. (Top right) High-resolution transmission electron microscopy reveals that the ultrathin nanowires are single crystals and exhibit smooth sidewalls. (Bottom) Photoluminescence spectra at 300 K from an ensemble of as-grown GaN nanowires (top spectrum) and from partially decomposed GaN nanowire ensembles with different average diameters. The free exciton transition shows a 42 meV blueshift with decreasing diameter as a result of dielectric confinement.

In this work, we demonstrate intense excitonic emission from bare GaN nanowires with diameters down to 6 nm. The large dielectric mismatch between the nanowires and vacuum greatly enhances the Coulomb interaction. The thinnest nanowires exhibit the strongest dielectric confinement and the highest radiative efficiency at 300 K. In situ monitoring of the fabrication of these structures allows one to accurately control the degree of dielectric enhancement. These ultrathin nanowires may constitute the basis for the fabrication of advanced low-dimensional structures with an unprecedented degree of confinement.

1 Author J. K. Zettler , P. Corfdir , C. Hauswald , E. Luna , U. Jahn , T. Flissikowski , E. Schmidt , C. Ronning , A. Trampert , L. Geelhaar , H. T. Grahn , O. Brandt , S. Fernández-Garrido

Observation of dielectrically confined excitons in ultrathin GaN nanowires up to room temperature

Source Nano Lett. , 16 , 973 ( 2016 )
DOI : 10.1021/acs.nanolett.5b03931 | 2739 Cite : Bibtex RIS
J. K. Zettler, P. Corfdir, C. Hauswald, E. Luna, U. Jahn, T. Flissikowski, E. Schmidt, C. Ronning, A. Trampert, L. Geelhaar, H. T. Grahn, O. Brandt, and S. Fernández-Garrido