Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 4: Focus Session (with TT): Functional semiconductor nanowires I
HL 4.2: Talk
Monday, March 16, 2015, 10:00–10:15, EW 201
Selective Area Growth of GaN Nanowires and Nanotubes — •Martin Hetzl1, Fabian Schuster1, Saskia Weiszer1, Jose A. Garrido1, María de la Mata2, Jordi Arbiol2, and Martin Stutzmann1 — 1Walter Schottky Institut and Physics Department, Technische Universität München, Garching, Germany — 2Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Bellaterra, Spain
Selective area growth (SAG) of GaN nanowires (NWs) by molecular beam epitaxy has been investigated in a systematic way. A high uniformity of SAG NWs and a complete suppression of unintentional growth has been achieved. The nucleation sites were predefined by a titanium mask structured by e-beam lithography. The underlying growth kinetics will be addressed by varying the substrate temperature, the III/V-ratio, the growth time and the NW arrangement. For that, diamond (111) substrates have been used as a model material. However, successful transfer of SAG on Si (111), c-plane sapphire and other substrates confirms the general validity of the presented growth mechanism. Scanning transmission electron microscopy has been performed to investigate the structural quality of the NWs and to determine the polarity of the wurtzite lattice. At lower temperatures, so called "tripods" instead of NWs can occur, which result from large GaN zinc blende nuclei. The exact NW arrangement changes the local III/V-ratio. This has been used to force a transition from GaN NW to nanotube growth, leading to a much higher effective surface-to-volume ratio. The controllability of SAG GaN NWs represents an important step towards NW-based devices, e.g. for optoelectronics, sensing or catalysis.