18. Apr. 2013, 16:15 Uhr, Gebäude NW1, Raum H3
GaN Nanowires - growth, optical properties and the route towards LED applications
Prof. Dr. Henning Riechert, Paul-Drude-Institut für Festkörperelektronik, Berlin
Semiconductor nanowires are nanostructures with diameters of the order of 50nm and up to several µm in length. They can be entirely defined by processes of crystal growth. Presently, such nanowire structures are receiving a lot of attention as potential building blocks for many types of nanoscale devices. In this talk I will discuss group-III nitride nanowires with respect to their possible impact on realising high quality material on Si, in particular for LED applications.
We grow such nanowires by molecular beam epitaxy (MBE) on bare Si surfaces without any aid by prestructuring or coverage by foreign materials. I will at first illustrate the factors that govern the nucleation process and the formation of the initial nanowire diameter on Si. This will include a brief excursion into nucleation theory.
In order to assess the usefulness of such structures, some results on structural and luminescence properties will be presented. They will illustrate that despite the high surface-to-volume ratio, the luminescence of GaN nanowires can be very efficient, but also shows some features that are unusual compared to planar GaN layers.
In order to prepare test devices, we have grown p-i-n structures and processed these into arrays of LEDs and I will show results on electro-luminescence as well as an analysis of their efficiency.
Looking into the future, it has to be questioned if the statistical nucleation process can be sufficiently controlled in order to lead to a viable technology. To address this issue, I will present some promising results of our efforts to achieve a controlled positioning of GaN nanowires by selective area growth.