S. Hagedorn, A. Knauer, F. Brunner, A. Mogilatenko, U. Zeimer, M. Weyers

Published in:

J. Cryst. Growth, vol. 479, pp. 16-21 (2017).

Abstract:

In this study we show how to realize a self-assembled nano-patterned sapphire surface on 2 inch diameter epi-ready wafer and the subsequent AlN overgrowth both in the same metal-organic vapor phase epitaxial process. For this purpose in-situ annealing in H₂ environment was applied prior to AlN growth to thermally decompose the c-plane oriented sapphire surface. By proper AlN overgrowth management misoriented grains that start to grow on non c-plane oriented facets of the roughened sapphire surface could be overcome. We achieved crack-free, atomically flat AlN layers of 3.5 µm thickness. The layers show excellent material quality homogeneously over the whole wafer as proved by the full width at half maximum of X-ray measured x-rocking curves of 120 arcsec to 160 arcsec for the 002 reflection and 440 arcsec to 550 arcsec for the 302 reflection. The threading dislocation density is 2 * 10⁹ cm^-2 which shows that the annealing and overgrowth process investigated in this work leads to cost-efficient AlN templates for UV LED devices.

Keywords:

A1. Substrate; A3. Metalorganic vapor phase epitaxy; B1. Nitrides; B1. Sapphire; B3. Light emitting diodes.

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