AlN overgrowth of nano-pillar-patterned sapphire with different offcut angle by metalorganic vapor phase epitaxy
S. Waldea, S. Hagedorna, P.-M. Coulonb,c, A. Mogilatenkoa, C. Netzela, J. Weinricha, N. Susilod, E. Zifferd, L. Matiwee, C. Hartmanne, G. Kuschf, A. Alasmarif, G. Naresh-Kumarf, C. Trager-Cowanf, T. Wernicked, T. Straubingere, M. Bickermanne, R.W. Martinf, P.A. Shieldsb,c, M. Kneissla,d, M. Weyersa
Published in:
J. Cryst. Growth, vol. 531, pp. 125343 (2020).
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 109cm-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%).
a Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
b Centre of Nanoscience & Nanotechnology, University of Bath, Bath BA2 7AY, UK
c Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK
d Institute of Solid State Physics, Technical University Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
e Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
f Department of Physics, SUPA, University of Strathclyde, 107 Rottenrow East, Glasgow G4 0NG, UK
Keywords:
A3. Metal organic vapor phase epitaxy; B1. Nitrides; B1. Sapphire; B3. Light emitting diodes
Copyright © 2019 Elsevier B.V. All rights reserved. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the Elsevier B.V.
Full version in pdf-format.