Investigation of inversion domain formation in AlN grown on sapphire by MOVPE
V. Kueller1, A. Knauer1, F. Brunner1, A. Mogilatenko1, M. Kneissl1,2, and M. Weyers1
Published in:
phys. stat. sol. (c), vol. 9, no. 3-4, pp. 496-498 (2012).
Abstract:
For certain growth conditions pronounced roughening has been observed for AlN layers grown on c-plane sapphire by metal-organic vapour phase epitaxy. TEM investigations revealed inversion domains correlated with the rough regions of the wafer. Al-polar material was found at hillocks and N-polar AlN in the valleys. We have investigated the early stages of growth and found three determining factors for the polarity development in AlN on c-plane sapphire: substrate treatment by NH3 (nitridation) or TMAl preflow, substrate treatment by annealing under H2 atmosphere and the influence of parasitic depositions in the reactor. We propose a correlation between the sapphire surface termination and the polarity of AlN. Oxygen termination of sapphire is suggested to lead to N-polarity and aluminium termination to Al-polar AlN. By optimising the reactor condition, substrate treatment and growth conditions, smooth Al-polar AlN layers were obtained for the subsequent growth of deep UV-LED heterostructures.
1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
2 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
Keywords:
AlN, CBED, inversion domains, MOVPE
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