Regensburg 2013 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 81: Focus Session: Extended defects in semi- and nonpolar GaN II
HL 81.1: Talk
Thursday, March 14, 2013, 14:45–15:00, H13
Energetics of step-edges and adatom kinetics on m-plane GaN surfaces: Implications for surface roughening and in-plane growth anisotropy. — •Andrew Duff1, Liverios Lymperakis2, and Jörg Neugebauer2 — 1Leibniz-Institut für Kristallzüchtung, Berlin — 2Max-Planck-Institut für Eisenforschung, Düsseldorf
Growth of non-polar m-plane GaN surfaces have attracted considerable interest due to the absence of polarization fields associated with the growth of polar surfaces. Typical m-plane GaN grown by MBE is characterized by a strong in-plane anisotropy in the form of elongated stripes along the [11-20] direction. However, recent growth experiments have demonstrated that atomically smooth m-plane surfaces can be achieved for growth on inclined substrates even under N-rich conditions in contrast to c-plane growth [1]. Full control of the growth of non-polar GaN surfaces requires an atomic-scale understanding of the mechanisms underlying the growth. Hence in the present work, step-edge energetics and adatom kinetics (i.e. Ehrlich-Schwoebel barriers), both in the presence of step-edges as well as on flat terraces, are investigated using density functional theory. Step-edge formation energies are found to be prohibitively large under both N- and Ga-rich conditions, consistent with the achievable smooth growth observed in both N- and Ga-rich regimes. The effect of temperature and the interplay between surface and step-edge energetics and adatom kinetics are addressed with kinetic Monte Carlo simulations, providing physical insight into the anisotropic character of non-polar growth of GaN.
[1] M. Sawicka et al, Phys. Rev. B 83, 245434 (2011).