N. Zainal^1,2, S. Hagedorn¹, C. Netzel¹, A. Mogilatenko¹, M. Schön¹, and M. Weyers¹

Published in:

phys. stat. sol. (a), vol. 220, no. 11, pp. 2300083, doi:10.1002/pssa.202300083 (2023).

Abstract:

High-temperature annealing (HTA) is a powerful technique to decrease dislocation density in AlN, which can also be applied on AlGaN. This work investigates the impact of using sapphire and AlN as a material cover during the face-to-face HTA process on Al_xGa_1-xN (0.55 < x < 0.93) properties. Before HTA, the threading dislocation density (TDD) in the AlGaN for all x_Al was about 6.0 × 10⁹ cm^-2. Meanwhile, after HTA, the sapphire cover led to a further reduction of the TDD at 5.7 × 10⁹ cm^-2 for the lowest x_Al and 1.4 × 10⁹ cm^-2 for the highest x_Al in comparison to the AlN cover. In most cases, strain relaxation increased by HTA, especially with the sapphire cover. Furthermore, increased optical absorption in HTA AlGaN can be lessened by the sapphire cover. Such absorption compromises the performance of UV LEDs which usually emit through the substrate. These advantages of sapphire over AlN as the cover in the HTA process are associated with additional oxygen incorporation into the AlGaN, most probably from the surface of the sapphire cover.

Keywords:

AlGaN, Ga loss, high-temperature annealing, metalorganic vapor phase epitaxy, oxygen incorporation

© 2023 The Authors. 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-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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