S. Hagedorn^a, T. Kolbe^a, A. Mogilatenko^a,b, C. Netzel^a, M. Schön^a, and M. Weyers^a

Published in:

phys. stat. sol. (a), vol. 222, no. 15, pp. 2500336, doi:10.1002/pssa.202500336 (2025).

Abstract:

The threading dislocation density (TDD) of epitaxially grown AlN layers on sapphire substrates can be significantly decreased by high-temperature annealing (HTA). This study employs a process to improve the material quality of such AlN layers that comprises two AlN growth steps and two HTA steps. While the first AlN growth and subsequent annealing ensure an initial base TDD of 6 × 10⁸ cm^-2 for all samples, the subsequent AlN growth on these low TDD layers is varied in terms of silicon doping and layer thickness. Annealing of the doped and undoped samples reveals that both the silicon doping and an increase in AlN layer thickness lead to a further decrease in TDD down to 1.6 × 10⁸ cm^-2 without impairing the ultraviolet transparency. The impact of such improved AlN templates on the performance of ultraviolet-C (UVC) light-emitting diodes (LEDs) emitting around 234 nm is examined. It is found that a decrease in TDD from 4.9 × 10⁸ cm^-2 down to 2.9 × 10⁸ cm^-2 leads to an increase in optical power by a factor of 1.4. For AlN templates with even lower TDD, no further increase in optical power of the far-UVC LEDs is observed, which can be related to dislocation half-loop formation close to the active region.

Keywords:

AlN template, high-temperature annealing, high-temperature annealing, silicon doping, ultraviolet light-emitting diode

©2025 The Author(s). physica status solidi (a) applications and materials science published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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