Finnish team grows GaAs and InP nanowires side by side
Dual-type nanowire arrays could be used in applications such as LEDs and solar cells
Researchers at Aalto University, Finland have developed a new method to implement different types of nanowires side-by-side into a single array on a single substrate. The new technique makes it possible to use different semiconductor materials for the different types of nanowires.
In their study, published in the Nano Letters journal on 5 February 2015, the researchers demonstrated GaAs and InP nanowires grown side by side.
"We have succeeded in combining nanowires grown by the VLS (vapour-liquid-solid) and SAE (selective-area epitaxy) techniques onto the same platform. The difference compared with studies conducted previously on the same topic is that in the dual-type array the different materials do not grow in the same nanowire, but rather as separate wires on the same substrate", says Docent Teppo Huhtio.
The new fabrication process has many phases. First, gold nanoparticles are spread on a substrate. Next, the substrate is coated with SiO, into which small holes are then patterned using electron beam lithography. In the first step of growth, (SAE), nanowires grow from where the holes are located, after which the silicon oxide is removed. In the second phase different types of nanowires are grown with the help of the gold nanoparticles (VLS). The researchers used an MOVPE reactor.
"In this way we managed to combine two growth methods into the same process", says doctoral candidate Joona-Pekko Kakko.
"We noticed in optical reflection measurements that light couples better to this kind of combination structure. For instance, a solar cell has less reflection and better absorption of light", Huhtio adds.
In addition to solar cells and LEDs, the researchers also see good applications in thermoelectric generators. Further processing for component applications has already begun.
'Fabrication of Dual-Type Nanowire Arrays on a Single Substrate' by Joona-Pekko Kakko et al, Nano Lett., Article ASAP DOI: 10.1021/nl504308x
