Florian Pantle1,Max Kraut1,Simon Wörle1,Elise Sirotti1,Andreas Zeidler1,Felix Eckmann1,Martin Stutzmann1
Walter Schottky Institute1
Florian Pantle1,Max Kraut1,Simon Wörle1,Elise Sirotti1,Andreas Zeidler1,Felix Eckmann1,Martin Stutzmann1
Walter Schottky Institute1
(In)GaN-based nanowires and nanofins are promising candidates for solar-to-fuel technologies due to their high surface-to-volume ratio, excellent crystal quality and tunable band gap with favorable band edge positions for water splitting and CO<sub>2 </sub>reduction reactions. Regarding this application, a thorough understanding of the interaction between the exposed crystal facets and the environment is crucial, as ambient molecules influence the electronic states at the surface and the charge carrier recombination. Investigations of the photoluminescence response of (In)GaN nanostructures to various atmospheres is a powerful tool to investigate their environmental interaction and stability.<sup>[1,2]</sup><br/>In this study, we investigate the role of the main air constituents nitrogen, oxygen and water on the efficiency of radiative recombination in GaN nanostructures grown by molecular beam epitaxy as a function of different surface treatments and at temperatures up to 200°C. Oxygen and water exposures result in a complex behavior as they can both act quenching and enhancing on the photoluminescence intensity, dependent on the temperature. For oxygen, we observe these characteristics already for low concentrations of below 0.5% in dry 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. 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.<sup>[3]</sup><br/>This knowledge about the impact of ambient molecules on the charge carrier dynamics and the electronic band bending is necessary for the development of efficient and simultaneous stable photocatalytic devices.<br/> <br/>[1] M. Hetzl, et al., Journal of Applied Physics 124, 35704 (2018)<br/>[2] K. Maier, et al., ACS Sensors 3, 2254 (2018)<br/>[3] M. Kraut, et al., Nanotechnology 32, 495703 (2021)