Silicon is a naturally occurring material commonly used as a semiconductor in electronic devices; however, researchers have exhausted the potential of devices with semiconductors made of silicon only. These devices are limited by silicon’s carrier mobility — the speed at which a charge moves through the material — and indirect bandgap, which limits its ability to release and absorb light.
Researchers have engineered a silicon-graphene device that can transmit radio frequency waves in less than a picosecond at a sub-terahertz bandwidth for future optoelectronic applications. The team combined silicon with graphene, which has more favorable properties. Compared to silicon, graphene has better carrier mobility and direct bandgap and allows for faster electron transmission and better electrical and optical properties. By combining silicon with graphene, scientists may be able to continue to utilize technologies that are already used with silicon devices — they would just work faster with the silicon-graphene combination.
To combine silicon with graphene, a new method was developed that places the graphene in the p-i-n junction, an interface between the materials. This optimized the structure in a way that improves the responsivity and speed of the device. The method is robust and could be easily applied by other researchers. The process takes place on a 12” wafer of thin material and utilizes components that are smaller than a millimeter each.
The combination of silicon and graphene can be used as a photodetector — which senses light and produces current — with more bandwidth and a lower response time than current offerings.