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Publication - Dr Filip Gucmann

    Evidence of relationship between strain and In-incorporation

    Growth of N-polar In-rich InAlN buffer layer by OMCVD

    Citation

    Chauhan, P, Hasenöhrl, S, Dobročka, E, Chauvat, MP, Minj, A, Gucmann, F, Vančo, &#x, Ko;váč, J, Jr., Kret, S, Ruterana, P, Kuball, M, Šiffalovič, P & Kuzmík, J, 2019, ‘Evidence of relationship between strain and In-incorporation: Growth of N-polar In-rich InAlN buffer layer by OMCVD’. Journal of Applied Physics, vol 125.

    Abstract

    Two I n x A l 1 - x N layers were grown simultaneously on different substrates [sapphire (0001) and the Ga-polar GaN template], but under the same reactor conditions, they were employed to investigate the mechanism of strain-driven compositional evolution. The resulting layers on different substrates exhibit different polarities and the layer grown on sapphire is N-polar. Moreover, for the two substrates, the difference in the degree of relaxation of the grown layers was almost 100%, leading to a large In-molar fraction difference of 0.32. Incorporation of In in I n x A l 1 - x N layers was found to be significantly influenced by the strain imposed by the under-layers. With the evolutionary process of In-incorporation during subsequent layer growth along [0001], the direction of growth was investigated in detail by Auger electron spectroscopy. It is discovered that the I n 0.60 A l 0.40 N layer grown directly on sapphire consists of two different regions with different molar fractions: the transition region and the uniform region. According to the detailed cross-sectional transmission electron microscopy, the transition region is formed near the hetero-interface due to the partial strain release caused by the generation of misfit-dislocations. The magnitude of residual strain in the uniform region decides the In-molar fraction. I n x A l 1 - x N layers were analyzed by structural and optical characterization techniques. Our present work also shows that a multi-characterization approach to study I n x A l 1 - x N is a prerequisite for their applications as a buffer layer.

    Full details in the University publications repository