Sunday, May 31, 2015

Epitaxial growth of GaN nanowires on metallic TiN by Paul-Drude-Institut, Berlin

Paul-Drude-Institut für Festkörperelektronik in Berlin has recently published a paper (below) on how to grow GaN Nanowires on TiN. From a silicon based semiconductor device perspective this is very interesting results since TiN can be used to make ohmic contact to silicon. For instance the is used in most DRAM Capacitor cells today where the word line is connected by a TiN/Ti/TiSi/Si ohmic contact. This technology was invented by Qimonda - The buried Word Line technology that was introduced at 65 nm and has been transferred to many other companies since then (Winbond, Micron, Elpida, ...). Or as the researchers at the Paul-Drude-Institut states:  

"The freedom to employ metallic substrates for the epitaxial growth of semiconductor nanowires in high structural quality may enable novel applications that benefit from the associated high thermal and electrical conductivity as well as optical reflectivity."


Epitaxial Growth of GaN Nanowires with High Structural Perfection on a Metallic TiN Film 

M. Wölz , C. Hauswald , T. Flissikowski , T. Gotschke , S. Fernández-Garrido , O. Brandt , H. T. Grahn , L. Geelhaar *, and H. Riechert 
Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.5b00251 
Publication Date (Web): May 22, 2015


Vertical GaN nanowires are grown in a self-induced way on a sputtered Ti film by plasma-assisted molecular beam epitaxy. Both in situ electron diffraction and ex situ ellipsometry show that Ti is converted to TiN upon exposure of the surface to the N plasma. In addition, the ellipsometric data demonstrate this TiN film to be metallic. The diffraction data evidence that the GaN nanowires have a strict epitaxial relationship to this film. Photoluminescence spectroscopy of the GaN nanowires shows excitonic transitions virtually identical in spectral position, line width, and decay time to those of state-of-the-art GaN nanowires grown on Si. Therefore, the crystalline quality of the GaN nanowires grown on metallic TiN and on Si is equivalent. The freedom to employ metallic substrates for the epitaxial growth of semiconductor nanowires in high structural quality may enable novel applications that benefit from the associated high thermal and electrical conductivity as well as optical reflectivity.