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Helge Weman: Epitaxial growth of semiconductor nanostructures on graphene

posted 2 Jun 2017, 02:14 by Peter Boggild
NTNU-Trondheim and CrayoNano AS, Norway

We have recently developed a generic atomic model, which describes the epitaxial growth of semiconductor nanostructures on graphene that is applicable to all conventional semiconductor materials[1,2]. The model was first verified by cross-sectional transmission electron microscopy studies of GaAs nanowires that grow epitaxially and dislocation-free on graphene. Recently we have also shown the vertical growth of dislocation-free GaN nanowires on graphene [3]. The epitaxial growth of semiconductor nanostructures on graphene is very appealing for device applications since graphene can function not only as a replacement of the semiconductor substrate but in addition as a transparent and flexible electrode for e.g. solar cells and LEDs.

For deep ultraviolet AlGaN based LEDs which are in huge need for various disinfection and sterilization purposes, the concept offers a real advantage over present thin film-based technology. Such thin film UV LEDs are today very expensive and inefficient due to the lack of a good transparent electrode (ITO is absorbing in deep UV), the high dislocation density in the active thin film layers, low light extraction efficiency, and the use of very expensive semiconductor substrates or buffer layers of AlN. The spin-off company CrayoNano are now developing UV LEDs based on the growth of AlGaN nanostructures on graphene, which potentially can overcome these problems, as will be further discussed in my talk.

1. A.M. Munshi, D.L. Dheeraj, V.T. Fauske, D.C. Kim, A.T.J. van Helvoort, B.O. Fimland, and H. Weman, Nano Letters 12, 4570 (2012).
2. A.M. Munshi and H. Weman, Phys. Status Solidi RRL 7, 713 (2013). (Review)
3. M. Heilmann, A.M. Munshi, G. Sarau, M. Göbelt, C. Tessarek, V.T. Fauske, A.T.J. van Helvoort, J. Yang, M. Latzel, B. Hoffmann, G. Conibeer, H. Weman, and S. Christiansen,
Nano Letters 16, 3524 (2016).

Dr. Helge Weman is a professor in nano-electronics at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. He received his PhD in semiconductor physics in 1988 from Linköping University, Sweden. During his career, he has held various positions at UCSB, NTT, EPFL and IBM Res. Lab Zurich. Since 2005 Weman is leading a research group at NTNU on III-V semiconductor nanowires grown on Si and graphene for use in optoelectronic applications. In June 2012 he founded CrayoNano AS who are now developing deep UV LEDs using AlGaN nanostructures grown on graphene. He is the coordinator of the M-era.Net project “Semiconductor Nanowire/Graphene Hybrids for High-Efficiency LEDs” consisting of academic and industrial partners from Norway and South Korea. At CrayoNano he is also partner of the EUROSTAR project “CMOS Fab-compatible Graphene”. Since 2010 Dr. Weman is a member of the Norwegian Academy of Technical Sciences (NTVA).