background

Photonics is a subject that studies the behavior and application of photons as information and energy carriers. Photonics and its related technologies, namely, photon technology, have rich connotations and broad application prospects. If you use smart phones, laptops and tablets, you are expected to benefit from photonics research.

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Recently, a team led by Tingyi Gu, an assistant professor in the Department of Electrical and Computer Engineering at the University of Delaware, USA, is developing cutting-edge technologies in photonic devices, which can make communication between devices and users faster.

Recently, the research team designed a "silicon-graphene" device, which can emit radio waves within one picosecond with a bandwidth of Asia-Pacific Hertz. This can not only carry more information, but also be faster. Their research was recently published in ACS Journal of Applied Electronic Materials.

Mao Dun, the first author and graduate student, said: "In this study, we have carefully studied the bandwidth limitation of silicon photonic devices integrated with graphene for future photoelectric applications."

technology

Silicon is a very rich material produced in nature and is usually used as a semiconductor in electronic equipment. However, researchers have exhausted the potential of semiconductor devices made only of silicon. These devices are limited by the carrier mobility (the speed of charge passing through the material) and indirect band gap (which limits the ability to release and absorb light) of silicon.

Now, Gu's team combines silicon with a material with more beneficial properties (two-dimensional material graphene). Two-dimensional materials are named after only one layer of atoms. Compared with silicon, graphene has better carrier mobility and direct band gap, which makes electron transport faster and has better electrical and optical properties. By combining silicon with graphene, scientists will be able to continue to use the technology already used in silicon devices, and the combination of silicon and graphene makes the operation faster. Thomas Kananen, a doctoral student, said, "By studying the characteristics of materials, can we do more than we do now? This is what we want to find out. "

In order to combine silicon with graphene, the team adopted a method they are developing. A paper published in the journal npj 2D Materials and Applications describes this method. The research team placed graphene in a special place, the so-called "p-i-n junction". It is the interface between materials. By placing graphene on the "p-i-n junction", the team optimized this structure in a way that can improve responsiveness and equipment speed.

This method is robust and easy to be adopted by other researchers. The process is produced on 12 inch ultra-thin wafer, and components smaller than one millimeter are used. Some parts are produced in commercial factories. Other work was carried out in the nano-manufacturing factory of the University of Delaware, and Matt Doty, an associate professor in the Department of Materials Science and Engineering, was the head of the factory.

Dottie said: "The University of Delaware Nanofabrication Facility (UNDF) is a factory supported by employees, which enables users to manufacture devices with a length of 7 nanometers, which is about one tenth of the diameter of human hair. Founded on 20 16, UNDF has brought new research directions to a series of fields from optoelectronics to biomedicine to plant science. "

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After silicon is combined with graphene, it can be used as a photodetector, which can sense light and generate current. Compared with the existing scheme, it has wider bandwidth and shorter response time. All these researches mean that the future will bring cheaper and faster wireless devices. Tian Li, a postdoctoral researcher and the first author of the paper published in the journal npj 2D Materials and Applications, said: "It can make the network stronger, better and cheaper. This is the focus of photonics. "

Now, the team is considering expanding the application of this material. Gu said: "We are looking for more components based on similar structures."

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reference data

1 https://www . udel . edu/u daily/20 19/March/ting y-gu-silicon-graphene-devices/

Mao Dun, Thomas Carnanning, anish Kumar Soman, Jeffrey Hinsky, Nicholas Petrone, James Horn, Gu Tingyi. Bandwidth limitation of direct contact graphene-silicon optoelectronic devices. ACS Applied Electronic Materials, 2019; 1(2): 172 DOI: 10. 102 1/acsaelm . 8b 000 15