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Author: Trampert, Achim × End date: 2023 × Start date: 2021 × DDC: 530 × Publisher: Weinheim : Wiley-VCH × WGL Institute: PDI ×

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    Self-Assembly of Well-Separated AlN Nanowires Directly on Sputtered Metallic TiN Films
    (Weinheim : Wiley-VCH, 2020) Azadmand, Mani; Auzelle, Thomas; Lähnemann, Jonas; Gao, Guanhui; Nicolai, Lars; Ramsteiner, Manfred; Trampert, Achim; Sanguinetti, Stefano; Brandt, Oliver; Geelhaar, Lutz
    Herein, the self-assembled formation of AlN nanowires (NWs) by molecular beam epitaxy on sputtered TiN films on sapphire is demonstrated. This choice of substrate allows growth at an exceptionally high temperature of 1180 °C. In contrast to previous reports, the NWs are well separated and do not suffer from pronounced coalescence. This achievement is explained by sufficient Al adatom diffusion on the substrate and the NW sidewalls. The high crystalline quality of the NWs is evidenced by the observation of near-band-edge emission in the cathodoluminescence spectrum. The key factor for the low NW coalescence is the TiN film, which spectroscopic ellipsometry and Raman spectroscopy indicate to be stoichiometric. Its metallic nature will be beneficial for optoelectronic devices using these NWs as the basis for (Al,Ga)N/AlN heterostructures emitting in the deep ultraviolet spectral range.
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    The Interaction of Extended Defects as the Origin of Step Bunching in Epitaxial III–V Layers on Vicinal Si(001) Substrates
    (Weinheim : Wiley-VCH, 2019) Niehle, Michael; Rodriguez, Jean-Baptiste; Cerutti, Laurent; Tournié, Eric; Trampert, Achim
    Several nanometer high steps are observed by (scanning) transmission electron microscopy at the surface and interfaces in heteroepitaxially grown III–Sb layers on vicinal Si(001) substrates. Their relations with antiphase boundaries (APBs) and threading dislocations (TDs) are elaborated. An asymmetric number density of TDs on symmetry-equivalent {111} lattice planes is revealed and explained according to the substrate miscut and the lattice misfit in the heteroepitaxial material system. Finally, a step bunching mechanism is proposed based on the interplay of APBs, TDs, and the vicinal surface of the miscut substrate.