Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866929230491680768 |
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| author | John, Philipp Ruiz, Mikel Gómez van Deurzen, Len Lähnemann, Jonas Trampert, Achim Geelhaar, Lutz Brandt, Oliver Auzelle, Thomas |
| author_facet | John, Philipp Ruiz, Mikel Gómez van Deurzen, Len Lähnemann, Jonas Trampert, Achim Geelhaar, Lutz Brandt, Oliver Auzelle, Thomas |
| contents | We study the molecular beam epitaxy of AlN nanowires between 950 and 1215 °C, well above the usual growth temperatures, to identify optimal growth conditions. The nanowires are grown by self-assembly on TiN(111) films sputtered onto Al$_2$O$_3$. Above 1100 °C, the TiN film is seen to undergo grain growth and its surface exhibits {111} facets where AlN nucleation preferentially occurs. Modelling of the nanowire elongation rate measured at different temperatures shows that the Al adatom diffusion length is maximised at 1150 °C, which appears to be the optimum growth temperature. However, analysis of the nanowire luminescence shows a steep increase in the deep-level signal already above 1050 °C, associated with O incorporation from the Al$_2$O$_3$ substrate. Comparison with AlN nanowires grown on Si, MgO and SiC substrates suggests that heavy doping of Si and O by interdiffusion from the TiN/substrate interface increases the nanowire internal quantum efficiency, presumably due to the formation of a SiN$_x$ or AlO$_x$ passivation shell. The outdiffusion of Si and O would also cause the formation of the inversion domains observed in the nanowires. It follows that for optoelectronic and piezoelectric applications, optimal AlN nanowire ensembles should be prepared at 1150 °C on TiN/SiC substrates and will require an ex situ surface passivation. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2306_09184 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires John, Philipp Ruiz, Mikel Gómez van Deurzen, Len Lähnemann, Jonas Trampert, Achim Geelhaar, Lutz Brandt, Oliver Auzelle, Thomas Materials Science We study the molecular beam epitaxy of AlN nanowires between 950 and 1215 °C, well above the usual growth temperatures, to identify optimal growth conditions. The nanowires are grown by self-assembly on TiN(111) films sputtered onto Al$_2$O$_3$. Above 1100 °C, the TiN film is seen to undergo grain growth and its surface exhibits {111} facets where AlN nucleation preferentially occurs. Modelling of the nanowire elongation rate measured at different temperatures shows that the Al adatom diffusion length is maximised at 1150 °C, which appears to be the optimum growth temperature. However, analysis of the nanowire luminescence shows a steep increase in the deep-level signal already above 1050 °C, associated with O incorporation from the Al$_2$O$_3$ substrate. Comparison with AlN nanowires grown on Si, MgO and SiC substrates suggests that heavy doping of Si and O by interdiffusion from the TiN/substrate interface increases the nanowire internal quantum efficiency, presumably due to the formation of a SiN$_x$ or AlO$_x$ passivation shell. The outdiffusion of Si and O would also cause the formation of the inversion domains observed in the nanowires. It follows that for optoelectronic and piezoelectric applications, optimal AlN nanowire ensembles should be prepared at 1150 °C on TiN/SiC substrates and will require an ex situ surface passivation. |
| title | Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires |
| topic | Materials Science |
| url | https://arxiv.org/abs/2306.09184 |