Strained nanowire has tunable electroptic properties
Researchers from IBM Research Zurich and the Norwegian University of Science and Technology (NTNU) at Trondheim have shown that a small strain on gallium arsenide nanowires can cause them to function efficiently as a single light-emitting diode or a photodetector. This is facilitated by an unnatural hexagonal crystal structure, referred to as wurtzite, which the NTNU researchers have succeeded in growing at NTNU.
In thin films of gallium arsenide, the atoms are typically in a cubic arrangement. When the researchers manipulate the atom structure inside the nanowire, they can grow both cubic and hexagonal crystal structures. The two structures have different electrical and optical properties.
"In cooperation with IBM, we have now discovered that if we stretch these nanowires, they function quite well as light-emitting diodes. Also, if we press the nanowires, they work quite well as photodetectors. This is facilitated by the hexagonal crystal structure, called wurtzite. It makes it easier for us to change the structure to optimize the optical effect for different applications," said Helge Weman, a professor in the university’s Department of Electronics and Telecommunication, in a statement.
"It also gives us a much better understanding, allowing us to design the nanowires with a built-in compressive stress, for example to make them more effective in a solar cell. This can for instance be used to develop different pressure sensors, or to harvest electric energy when the nanowires are bent," Weman added.
CrayoNano AS, a startup company created by the Trondheim research group in 2012 plans to grow growing gallium nitride nanowires for use in white light-emitting diodes.
"When you pull the nanowire along its length, the nanowire is in a state that we call “direct bandgap” and it can emit light very efficiently; when instead you compress the length of the wire, its electronic properties change and the material stops emitting light. We call this state “pseudo-direct”: the III-V material behaves similarly to silicon or germanium and becomes a good light detector," said IBM scientist Giorgio Signorello in a separate statement.
The research is reported in a Nature Communications paper titled "Inducing a Direct-to-Pseudodirect Bandgap Transition in Wurtzite GaAs Nanowires with Uniaxial Stress."
Related links and articles:
News articles:
IBM shows key step to spintronic transistors
Researchers grow semiconductors on graphene
Arctic Silicon claims ADC low-power ground
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
