High-quality AlN grown on a thermally decomposed sapphire surface

• Published in: Journal of crystal growth 2017-12, Vol.479, p.16-21
• Main Authors: Hagedorn, S., Knauer, A., Brunner, F., Mogilatenko, A., Zeimer, U., Weyers, M.
• Format: Article
• Language: English
• Subjects: A1. Substrate; A3. Metalorganic vapor phase epitaxy; Aluminum nitride; Annealing; B1. Nitrides; B1. Sapphire; B3. Light emitting diodes; Crystals; Decomposition; Dislocation density; Light emitting diodes; Reflection; Sapphire; Studies; Thickness
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2017.09.019

•Self-assembled nano-scale patterning of sapphire in multiwafer MOVPE reactor.•MOVPE AlN growth on sapphire that had been roughened in-situ prior to growth.•Deposition of 3.5µm thick, smooth, c-plane oriented, crack free AlN.•Threading dislocation densities of 2∗109cm−2 homogeneously across 2inch wafer. In this study we show how to realize a self-assembled nano-patterned sapphire surface on 2inch 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 3.5µm 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 ω-rocking curves of 120arcsec to 160arcsec for the 002 reflection and 440arcsec to 550arcsec for the 302 reflection. The threading dislocation density is 2∗109cm−2 which shows that the annealing and overgrowth process investigated in this work leads to cost-efficient AlN templates for UV LED devices.