Influence of environmental conditions and surface treatments on the photoluminescence properties of GaN nanowires and nanofins

Max Kraut; Florian Pantle; Simon Wörle; Elise Sirotti; Andreas Zeidler; Felix Eckmann; Martin Stutzmann

doi:10.1088/1361-6528/ac1dd1

Influence of environmental conditions and surface treatments on the photoluminescence properties of GaN nanowires and nanofins

Nanotechnology. 2021 Sep 14;32(49). doi: 10.1088/1361-6528/ac1dd1.

Authors

Max Kraut¹, Florian Pantle¹, Simon Wörle¹, Elise Sirotti¹, Andreas Zeidler¹, Felix Eckmann¹, Martin Stutzmann¹

Affiliation

¹ Walter Schottky Institut and Physics Department, Technische Universität München, Am Coulombwall 4, D-85748 Garching, Germany.

PMID: 34399419
DOI: 10.1088/1361-6528/ac1dd1

Abstract

Due to their intrinsically large surface-to-volume ratio, nanowires and nanofins interact strongly with their environment. We investigate the role of the main air constituents nitrogen, oxygen and water on the efficiency of radiative recombination in GaN nanostructures as a function of different surface treatments and at temperatures up to 200 °C. Oxygen and water exposures exhibit a complex behavior as they can both act quenching and enhancing on the photoluminescence intensity dependent on the temperature. For oxygen, these characteristics are already observed for low concentrations of below 0.5% in nitrogen. While the photoluminescence intensity changes induced by oxygen occur independently of illumination, the influence of water is light-induced: it evolves within tens of seconds under ultraviolet light exposure and is heavily influenced by the nanostructure pre-treatment. In contrast to observations in dry atmospheres, water prevents a recovery of the photoluminescence intensity in the dark. Combined measurements of the electrical current through GaN nanofins and their photoluminescence intensity reveal the environmental influence on the interaction of non-radiative recombination processes and changes in the surface band bending of the nanostructures. Several investigated solvents show an enhancing effect on the PL intensity increase, peaking in c-hexane with a 26-fold increase after 6 min of light exposure. Stabilization of the PL intensity was achieved by a passivation of the GaN surface with Ga_xO_y, and ZnO shells. Surprisingly, Al₂O₃coatings resulted in a highly instable PL intensity during the first minutes of illumination. Our findings reveal the high importance of controlled environmental conditions for the investigation of nanostructures, especially when aimed at their applications in the fields of environmental sensing, photo-catalysis and light-emitting diodes.

Keywords: GaN; environmental influence; nanofins; nanowires; photoluminescence; sensing; surface band bending.

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