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

Walde, S. and Hagedorn, S. and Coulon, P.-M. and Mogilatenko, A. and Netzel, C. and Weinrich, J. and Susilo, N. and Ziffer, E. and Matiwe, L. and Hartmann, C. and Kusch, G. and Alasmari, A. and Naresh-Kumar, G. and Trager-Cowan, C. and Wernicke, T. and Straubinger, T. and Bickermann, M. and Martin, R. W. and Shields, P. A. and Kneissl, M. and 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. ISSN 0022-0248 (

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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 %).


Walde, S., Hagedorn, S., Coulon, P.-M., Mogilatenko, A., Netzel, C., Weinrich, J., Susilo, N., Ziffer, E., Matiwe, L., Hartmann, C., Kusch, G. ORCID logoORCID:, Alasmari, A. ORCID logoORCID:, Naresh-Kumar, G. ORCID logoORCID:, Trager-Cowan, C. ORCID logoORCID:, Wernicke, T., Straubinger, T., Bickermann, M., Martin, R. W. ORCID logoORCID:, Shields, P. A., Kneissl, M. and Weyers, M.;