AlN overgrowth of nano-pillar-patterned sapphire with different offcut angle by metalorganic vapor phase epitaxy

S. Walde, S. Hagedorn, P.-m. Coulon, A. Mogilatenko, C. Netzel, J. Weinrich, N. Susilo, E. Ziffer, L. Matiwe, C. Hartmann, Gunnar Kusch, A. Alasmari, G. Naresh-kumar, C. Trager-cowan, T. Wernicke, T. Straubinger, M. Bickermann, Robert W. Martin, P.a. Shields, M. KneisslM. Weyers

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Abstract

We present overgrowth of nano-patterned sapphire with different offcut angles by metalorganic vapor phase epitaxy. Hexagonal arrays of nano-pillars were prepared via Displacement Talbot Lithography and dry-etching. 6.6 µm crack-free and fully coalesced AlN was grown on such substrates. Extended defect analysis comparing X-ray diffraction, electron channeling contrast imaging and selective defect etching revealed a threading dislocation density of about 109 cm−2. However, for c-plane sapphire offcut of 0.2° towards m direction the AlN surface shows step bunches with a height of 10 nm. The detrimental impact of these step bunches on subsequently grown AlGaN multi-quantum-wells is investigated by cathodoluminescence and transmission electron microscopy. By reducing the sapphire offcut to 0.1° the formation of step bunches is successfully suppressed. On top of such a sample an AlGaN-based UVC LED heterostructure is realized emitting at 265 nm and showing an emission power of 0.81 mW at 20 mA (corresponds to an external quantum efficiency of 0.86%).
Original languageEnglish
Article number125343
JournalJournal of Crystal Growth
Volume531
Early online date13 Nov 2019
DOIs
Publication statusPublished - 1 Feb 2020

Cite this

Walde, S., Hagedorn, S., Coulon, P., Mogilatenko, A., Netzel, C., Weinrich, J., ... Weyers, M. (2020). AlN overgrowth of nano-pillar-patterned sapphire with different offcut angle by metalorganic vapor phase epitaxy. Journal of Crystal Growth, 531, [125343]. https://doi.org/10.1016/j.jcrysgro.2019.125343