Apr 16, 2013
Nanowires grown on polycrystalline silicon
III–V compound semiconductor nanowires, which have diameters on the nanometre scale, can be produced using a crystal growth technique and are often described as building blocks for next-generation LEDs. Further progress in developing low-cost LEDs is expected to follow the emergence of glass-based polycrystalline silicon (poly-Si) thin-film substrates for nanowire optical devices thanks to lower production costs, good compatibility with high-volume manufacturing processes for flat-panel displays and greater scalability compared with conventional LED structures formed on compound semiconductor substrates.
In a recent study, researchers at Hokkaido University in Japan have proposed and demonstrated GaAs nanowire fabrication on poly-Si substrates using selective-area metal organic vapour-phase epitaxy (SA-MOVPE). The key to obtaining nanowires on poly-Si was the use of a SiO2 mask layer with nanometre-scale openings. Under the appropriate growth conditions of MOVPE, GaAs crystal growth occurs only at the mask opening, where the poly-Si surface is exposed. The crystal growth can proceed in a similar way to on a single crystal substrate, when the size of mask opening is equivalent to that of a grain of poly-Si.
Evaluation of the grown shapes and growth characteristics revealed that GaAs nanowires grown on poly-Si substrates have the same growth mechanism as conventional GaAs NWs grown on single-crystalline GaAs or Si substrates. Experiments showed that the wire structure yield can be improved by increasing the Si grain size and/or increasing the Si deposition temperature. The growth model proposed for understanding nanowire growth on poly-Si is based on the mask opening size, the Si grain size, and the growth conditions. The ability to control the growth mode is promising for the formation of nanowires with complex structures on poly-Si thin layers.
The next target of this study is the formation of nanowires with complex structures, such as core-shell heterostructures and pn junctions, on poly-Si thin layers, and the realization of cost-effective and resource-efficient nanowire LEDs.
Additional details can be found in the journal Nanotechnology.
About the author
The work was performed at the Research Center for Integrated Quantum Electronics (RCIQE) and the Graduate School of Information Science and Technology, Hokkaido University. Keitaro Ikejiri is a PhD student at the Graduate School of Information Science and Technology at Hokkaido University. Fumiya Ishizaka is a masters course student at the Graduate School of Information Science and Technology at Hokkaido University. Dr Katsuhiro Tomioka is a researcher for the Japan Science and Technology Agency (JST)-PRESTO Program and for the Graduate School of Information Science and Technology at Hokkaido University. Prof. Takashi Fukui is director of the RCIQE and a professor at the Graduate School of Information Science and Technology at Hokkaido University.