CREDIT: Kathy F. Atkinson
If you use a smartphone, laptop, or tablet, then you benefit from research in photonics, light study. At the University of Delaware, a team led by Tingyi Gu, assistant professor of electrical and computer engineering, is developing innovative technology for photonics devices that could enable faster communication between devices and therefore the people using them.
Recently, the research group invented a silicon graphene device that can transfer radio frequency waves in less than picosecond in semi-subrahertz – that's a lot of information, fast. Their work is described in a newspaper published in the magazine Applied Electronic Materials ACS.
"In this work, we examined the bandwidth of the integrated silicon-integrated photonics for future optoelectronics applications," said Dun Mao, the first author of the paper.
Silicon is a naturally occurring material and is often used as semiconductors in electronic devices. However, researchers have exhausted the potential of devices with semiconductors having only made of silicon. These devices are limited by silicone carrier movement, the speed at which a charge moves through the material, and an indirect bandgap, which limits its ability to release and absorb light.
Now, the Gu team combines silicon with material with more favorable properties, the 2D material graphene. 2D materials get their name because they are only one layer of atoms. Compared with silicon, graphene has a better carrier movement and a direct bandgap and allows faster transfer of electrons and better electrical and optical properties. By combining silicon with graphene, scientists may be able to continue to use technologies that are already being used with silicone devices – they would only work faster with the gravel-silicon combination.
"Looking at the properties of the materials, can we do more than what we are working with? That's what we want to find out," says Thomas Kananen, the doctoral student.
To combine silicon with graphene, the team used an approach developed and described in a paper published in 2018 2D Materials and Application npj. The team set the graphene in a special place of the name of the p-to-n junction, the interface between the materials. By placing the graphene in the p-i-n junction, the team optimized the structure in a way that improved the responsibility and speed of the device.
This method is robust and other researchers could easily apply it. This process takes place on a 12 inch wafer of thin material and uses components less than one millimeter each. Some components were made in a commercial foundry. Another work was done at the US Nanofabation Facility, which is chaired by Matt Doty, associate science and materials science teacher.
"The US Neutralization Facility (UDNF) is a staff-backed facility that allows users to falsify devices as small as 7 nm, which is about 10,000 times less than human hair diameter," Doty said. "The UDNF, which opened in 2016, has enabled new research directions in areas ranging from optoelectronics to biomedicine to plant science."
The combination of silicon and graphene can be used as a photodector, sensing light and producing current, with more bandwidth and lower response time than current offerings. All this research could add to cheaper, faster, wireless devices in the future. "It can make the network stronger, better and cheaper," says post-doctoral connector and author of the first article of Npj 2D Materials and Application Tiantian Li. "That is a key point of photonics."
Now the team is thinking about ways to expand the use of this material. "We are looking at more components based on a similar structure," Gu said.
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