Nov 7 2017
In the 1830s, a mineral called perovskite was discovered in Russia and it is said to hold the key to the next stage in ultra-high-speed communications and computing.
University of Utah physics and astronomy Distinguished Professor Valy Vardeny, left, and University of Utah electrical and computer engineering professor Ajay Nahata have discovered that a special kind of perovskite, a combination of an organic and inorganic compound that has the same structure as the original mineral, can be layered on a silicon wafer to create a vital component for the communications system of the future. That system would use the terahertz spectrum, the next generation of communications bandwidth that uses light instead of electricity to shuttle data, allowing cellphone and internet users to transfer information a thousand times faster than today. (Photo Credit: Dan Hixon/University of Utah College of Engineering)
A team of researchers from the University of Utah’s departments of electrical and computer engineering and astronomy and physics have identified that a special type of perovskite, a mixture of an inorganic and organic compound has the same structure as the original mineral, and can be layered on a silicon wafer to develop an important component for the communications system of the future. That system would utilize the terahertz spectrum, the next generation of communications bandwidth that uses light rather than electricity to transfer data, allowing internet and cellphone users to transfer information a thousand times faster than what is achievable today.
This new research, led by University of Utah electrical and computer engineering professor Ajay Nahata and physics and astronomy Distinguished Professor Valy Vardeny, was published in the November 6 issue of the Nature Communications.
The terahertz range is a band between radio waves and infrared light and utilizes frequencies that span the range from 100 gigahertz to 10,000 gigahertz (a standard cellphone works at just 2.4 gigahertz). Scientists are investigating how to apply these light frequencies to convey data because of its remarkable potential for increasing the speeds of devices such as cellphones and internet modems.
Nahata and Vardeny found a crucial piece of that puzzle: By placing a distinct form of multilayer perovskite onto a silicon wafer, they can control terahertz waves traveling through it using a standard halogen lamp. Controlling the amplitude of terahertz radiation is vital because it is how data in such a communications system would be transferred.
Earlier attempts to achieve this have typically required the use of an expensive, high-power laser. What is unique about this demonstration is that it is not only the lamp power that allows for this modulation but also the particular color of the light. Therefore, they can put a variety of perovskites on the same silicon substrate, where each region could be manipulated by different colors from the lamp. This is not easily achievable when using conventional semiconductors such as silicon.
Think of it as the difference between something that is binary versus something that has 10 steps, silicon responds only to the power in the optical beam but not to the color. It gives you more capabilities to actually do something, say for information processing or whatever the case may be.
Professor Ajay Nahata, electrical and computer engineering department, University of Utah
This not only paves the way for making terahertz technologies a reality - resulting in next-generation communications systems and computing that is substantially faster - but also the process of layering perovskites on silicon becomes simple and economical using a technique known as “spin casting,” in which the material is placed on the silicon wafer by spinning the wafer and allowing centripetal force to disperse the perovskite uniformly.
Vardeny says what is unique about the type of perovskite they are utilizing is that it is an inorganic material like rock as well as organic like a plastic, making it easy to place on silicon while also having the optical properties essential to make this process doable.
“It’s a mismatch,” he said. “What we call a ‘hybrid.’”
Nahata says it is possibly a minimum of another 10 years before terahertz technology for communications and computing is used in commercial products, but this latest research is a major milestone to reaching there.
This basic capability is an important step towards getting a full-fledged communications system, if you want to go from what you’re doing today using a modem and standard wireless communications, and then go to a thousand times faster, you’re going to have to change the technology dramatically.
Professor Ajay Nahata, electrical and computer engineering department, University of Utah
The research paper was co-authored by students, Ashish Chanana, Yaxin Zhai, Sangita Baniya and Chuang Zhang.