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Tuned nanowire strain yields enhanced LEDs

Posted: 16 Apr 2014     Print Version  Bookmark and Share

Keywords:solar cells  LED lighting  nanowires 

NTNU researchers Dheeraj Dasa and Helge Weman have, in cooperation with IBM, discovered that gallium arsenide can be tuned with a small strain to function efficiently as a single light-emitting diode or a photodetector. The tuning is facilitated by the special hexagonal crystal structure, referred to as wurtzite, which the researchers have succeeded in growing in the MBE lab at NTNU.

The last few years have seen several breakthroughs in nanowire and graphene research at NTNU. In 2010, Professors Helge Weman, Bjrn-Ove Fimland and Ton van Helvoort and their academic group went public with their first groundbreaking discoveries within the field.

The researchers, who specialise on growing nanowires, had succeeded in controlling a change in the crystal structure during nanowire growth. By altering the crystal structure in a substance, i.e. changing the positions of the atoms, the substance can gain entirely new properties. The NTNU researchers discovered how to alter the crystal structure in nanowires made of gallium arsenide and other semiconductors.

Tuned nanowire strain yields enhanced LEDs

Figure 1: Dr. Dasa and Prof. Weman with a giant model of the wurtzite crystal structure.

"Our discovery was that we could manipulate the structure, atom by atom. We were able to manipulate the atoms and alter the crystal structure during the growth of the nanowires. This opened up for vast new possibilities. We were among the first in the world who were able to create a new gallium arsenide material with a different crystal structure," said Helge Weman at the Department of Electronics and Telecommunications.

The research group has received a lot of international attention for the graphene method. Helge Weman and his NTNU co-founders Bjrn-Ove Fimland and Dong-Chul Kim have established the company CrayoNano AS, working with a patented invention that grows semiconductor nanowires on graphene. The method is called molecular beam epitaxy (MBE), and the hybrid material has good electric and optical properties.


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