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DS: Fachverband Dünne Schichten
DS 6: Focus Session: Innovative GaN-based High-power Devices: Growth, Characterization, Simulation, Application 2
DS 6.2: Invited Talk
Monday, September 5, 2022, 15:30–16:00, H17
Ab-initio investigations of V-pits and nanopipes in GaN — •Liverios Lymperakis1,2, Su-Hyun Yoo2, and Jörg Neugebauer2 — 1Department of Physics, University of Crete, Heraklion, Greece — 2Computational Materials Design Department, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
Dislocations in nitrides constitute a long-standing and controversial topic. Nevertheless, screw dislocations in GaN have recently attracted considerable interest due to their potential effect on power electronic devices' performance. An intriguing feature of these dislocations is that they trigger the formation of V-pits and nanopipes in GaN. However, a full understanding of their origin, size, and shape is still lacking. The nucleation and properties of these defects are governed by the complex interplay between dislocation's strain and core energies, surface energies, and oversaturation. In the present work, we combine density functional theory calculations with elasticity theory and we shed light on the aforementioned interplay. Based on these calculations we derive phase diagrams that describe the equilibrium size and shape of V-pits and nanopipes as a function of the ambient growth conditions, i.e., the Ga and H chemical potentials as well as the oversaturation. Our calculations indicate that under H-rich conditions, V-pits and nanopipes can spontaneously form due to the preferential decoration of the bounding surfaces by hydrogen. Based on these results we will further discuss their electronic properties as well as their potential to preferentially accommodate impurities/dopants.