Norwegian University of Science and Technology (NTNU) researchers report they have patented and are commercializing gallium arsenide (GaAs) nanowires grown on graphene, a hybrid material with competitive properties. Semiconductors grown on graphene are expected to become the basis for new types of device systems, and could fundamentally change the semiconductor industry.
The new patented hybrid material offers excellent optoelectronic properties, says Professor Helge Weman, a professor at NTNU’s Department of Electronics and Telecommunications, and CTO and co-founder of the company created to commercialize the research, CrayoNano AS. “We have managed to combine low cost, transparency and flexibility in our new electrode,” he adds.
The patented method of growing semiconductor nanowires on atomically thin graphene uses molecular beam epitaxy (MBE) to grow the nanowires.
“We do not see this as a new product,” Weman says. “This is a template for a new production method for semiconductor devices. We expect solar cells and light emitting diodes to be first in line when future applications are planned.”
Sunny outlook for nanowires
“Graphene is experiencing tremendous attention worldwide,” Weman says. “Companies like IBM and Samsung are driving this development in the search for a replacement for silicon in electronics as well as for new applications, such as flexible touch screens for mobile phones. Well, they need not wait any more. Our invention fits perfectly with the production machinery they already have. We make it easy for them to upgrade consumer electronics to a level where design has no limits.”
This invention is thus thought to be an enabler for a future platform for electronics and optoelectronics devices. One possible device with very large market potential is a nanowire solar cell. This type of solar cell has the potential to be efficient, cheap and flexible at the same time. The invention also makes it possible to imagine a future with self-powered nanomachines and advanced 3D integrated circuits built on graphene and semiconductor nanowires, enabling smaller and more efficient electronics.
Weman himself envisions flexible self-powered consumer electronics integrated into everything from clothes to notepads, and of course traditional cell phones, tablets and exercise accessories.
“Semiconductors grown on graphene could become the basis for new types of device systems, and could transform the semiconductor industry by introducing graphene as a preferred substrate for many applications,” he says.
ABSTRACT – By utilizing the reduced contact area of nanowires, we show that epitaxial growth of a broad range of semiconductors on graphene can in principle be achieved. A generic atomic model is presented which describes the epitaxial growth configurations applicable to all conventional semiconductor materials. The model is experimentally verified by demonstrating the growth of vertically aligned GaAs nanowires on graphite and few-layer graphene by the self-catalyzed vapor–liquid–solid technique using molecular beam epitaxy. A two-temperature growth strategy was used to increase the nanowire density. Due to the self-catalyzed growth technique used, the nanowires were found to have a regular hexagonal cross-sectional shape, and are uniform in length and diameter. Electron microscopy studies reveal an epitaxial relationship of the grown nanowires with the underlying graphitic substrates. Two relative orientations of the nanowire side-facets were observed, which is well explained by the proposed atomic model. A prototype of a single GaAs nanowire photodetector demonstrates a high-quality material. With GaAs being a model system, as well as a very useful material for various optoelectronic applications, we anticipate this particular GaAs nanowire/graphene hybrid to be promising for flexible and low-cost solar cells.