By Josh Perry, Editor
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Scientists at the University of Delaware (Newark) developed a photonic device from silicon and graphene that transmits radio frequency waves in less than a picosecond at a sub-terahertz bandwidth, a significant enhancement in communications between devices.

If you use a smartphone, laptop, or tablet, then you benefit from research in photonics, the study of light. (University of Delaware)

The research team combined silicon with graphene to improve its carrier mobility and take advantage of its direct bandgap, according to a report from the university. The combined materials enhanced the capabilities of the device, offering a path forward after engineers had reached the limitations of silicon-based devices.

Graphene was placed in the p-i-n junction at the interface between the two materials to improve the structure of the device. “This process takes place on a 12-inch wafer of thin material and utilizes components that are smaller than a millimeter each. Some components were made at a commercial foundry,” the article explained.

Researchers believe this combination of materials can be used in photodetectors, and eventually to “cheaper, faster wireless devices.” The scientists are now looking at other applications to expand the impact of this material.

The research was recently published in ACS Applied Electronic Materials. The abstract stated:

“Electrically contacting layered materials on a complementary metal-oxide-semiconductor transistor (CMOS)-processed lateral silicon homojunction offers a new platform enabling postfabrication-free high-speed hybrid optoelectronic devices on chip.

“Understanding detailed junction formation and radiofrequency (RF) response on the multicomponent interface between directly contacted silicon nanophotonic devices and low-bandgap materials is essential for predicting the performance of those active components. Electrostatic carrier distribution as well as the dynamics of externally injected carriers are strongly influenced by spatially varying Schottky barriers on the vertical heterojunctions.

“In this work, we analyze the high-speed RF response of a graphene “bonded” lateral silicon p-i-n junction. The multijunction structure on the hybrid structure is parametrized by fitting a small-signal model to the broadband coherent radio frequency response of the hybrid device at a series of different carrier injection rates.

“By engineering the device dimensions, it is possible to suppress the resistance–capacitance delay to be less than a picosecond and enable sub-terahertz bandwidth operation.”