GaN nanowires: growth and applications

Blandine Alloing

Centre de Recherche sur l’Hétéroépitaxie et ses Applications (CNRS-CRHEA) Rue Bernard Grégory, 06560 Valbonne, France.

The 2014 Nobel Prize in physics has been attributed to the three inventors of the first efficient blue LED which has enabled bright and energy-saving white light sources. In the mid-1990s, I. Akasaki, H. Amano and S. Nakamura found the way to achieve the epitaxial growth and the doping of high quality nitride semiconductors that is Gallium Nitride (GaN) and its alloys with Aluminium and Indium. Since then, GaN is considered as the material of choice for optoelectronic applications as well as for high frequency devices. However the growth of this wide-bandgap material remains challenging: the lack of an adapted substrate results in a very large density of defects, in particular dislocations, stacking faults and cracks. Under these circumstances, the growth of nanostructures and in particular nanowires appears as an appealing means of circumventing the problem. First, these nanostructures present a low density of structural defects and an efficient elastic relaxation of strain by their lateral free-facets[Hug13], which should enable fundamentally more efficient devices. Second, their 1D geometry improves the light extraction and absorption efficiency making them suitable candidates for optoelectronic applications such as solar cells, LEDs or lasers. Furthermore, their high surface-to-volume ratio results in a high detection sensitivity and improved response time, which explains the important development of Nanowire-based sensors [Pea11][Hsu11][Pan13]. In this talk, some examples of application using GaN nanowires will be described and the activities done at CRHEA on the growth by metalorganic vapour phase epitaxy (MOVPE) and the characterization of GaN-based nanowires will be presented. Their structural and optical properties will be discussed based on transmission electron microscopy and cathodoluminescence experiments.

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