'Nearly Perfect' Crystals Could Advance Nano-Optoelectronics

Embedding “nearly perfect” semiconductor crystals in silicon nanowires solves a problem in the production of nano-optoelectronic components, according to a team of European researchers.

The crystals — made of indium arsenide (InAs) — possess extremely high electron mobility and could be useful in improving silicon-based CMOS technology, the team said. To date, integrating such crystals into nanowires has been difficult because crystal lattice mismatch always led to numerous defects.

An energy-dispersive x-ray spectroscope image shows an InAs nanocrystal (green-cyan) integrated in a silicon nanowire (blue). A sleeve of silicon oxide (red) can be seen outside the wire. Courtesy of TU Vienna and the Swiss Federal Institute of Technology.

The researchers used liquid-phase epitaxy to get around the problem. First, they introduced a determined number of atoms precisely into the liquid nanowires via ion beam synthesis. Next, they annealed the nanowires for 20 ms with a xenon flash lamp, creating a 15-nm-thick silicon oxide shell that maintained the form of the liquid nanowire.

“The atoms diffuse in the liquid-silicon phase so rapidly that within milliseconds they form flawless monocrystals delineated from their surroundings with nearly perfect interfaces,” said lead researcher Dr. Wolfgang Skorupa of Helmholtz-Zentrum Dresden-Rossendorf.

Going forward, the scientists want to introduce other compound semiconductors into silicon nanowires and also optimize the size and distribution of the crystals.

Researchers at the Vienna University of Technology, Maria Curie-Sklodowska University Lublin in Poland and the Swiss Federal Institute of Technology in Lausanne also collaborated on the project. The work was published in Nano Research (doi: 10.1007/s12274-014-0536-6).

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