Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 98: Nitrides: Bulk material, films, surfaces and quantum wells
HL 98.11: Talk
Friday, March 20, 2015, 12:15–12:30, EW 201
Influence of off-cut on the surface morphology and defect distribution of epitaxial laterally overgrown (ELO)-AlN — •Johannes Enslin1, Frank Mehnke1, Tim Wernicke1, Konrad Bellmann1, Arne Knauer2, Viola Kueller2, Anna Mogilatenko2, Markus Weyers2, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin, Germany — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
Smooth AlN layers on sapphire with low defect densities are essential for efficient light emitters in the UV-C spectral region between 200 nm and 280 nm. By growing AlN on patterned sapphire substrates (ELO) the threading dislocation density can be significantly reduced from 1010cm−2 to <109cm−2. However, the ELO-AlN surfaces often suffer from macrosteps with heights of 22 nm for an off-cut angle of 0.25∘ to the sapphire m-plane. In this paper, we study the influence of the sapphire substrate off-cut angle on the occurrence of macrosteps on ELO-AlN. For this purpose sapphire wafers with off-cut angles between 0.08∘±0.008∘ and 0.23∘±0.008∘ were overgrown. AFM analysis of the ELO-AlN surfaces revealed macrosteps for off-cut angles between 0.16∘ and 0.23∘ with step heights of 19 nm. For substrate off-cuts of <0.12∘ the surface exhibits a wavelike surface morphology with the periodicity of the ELO pattern and a peak to bottom ratio of 4 nm. The influence of the surface morphology on the defect distribution will be discussed.