Strain Engineering of 2D Materials Enables More Effortless Photodetection

Using a 2D material and an approach it calls “strainoptronics,” a George Washington University research team created a photodetector that can operate with high efficiency at the wavelength of 1550 nm, a spectral region that offers low-loss transmission and optical gain.

The researchers stretched an ultrathin layer of molybdenum telluride on top of a nanoscale silicon photonic waveguide. Using strain engineering, they altered the physical properties of the 2D material to shrink the electronic bandgap. This approach allowed the device to operate at near-infrared wavelengths — specifically, at the telecommunication C-band-relevant wavelength that is around 1550 nm.

Artistic representation of a strain-engineered 2D photodetector on silicon photonic circuit. Courtesy of Mario Miscuglio/George Washington University.

According to the researchers, no efficient photodetector in the telecommunication C-band has yet been made using 2D transition metal dichalcogenide materials, due to the large optical bandgap in these materials. Because 2D materials exhibit strong optical absorption, a 2D-material-based photodetector could provide better photoconversion and hence more efficient data transmission and telecommunications.

“We not only found a new way to engineer a photodetector, but also discovered a novel design methodology for optoelectronic devices, which we termed strainoptronics,” professor Volker Sorger said. “These devices bear unique properties for optical data communication and for emerging photonic artificial neural networks used in machine learning and AI.”

The researchers found that the amount of strain that the 2D semiconductor materials could bear was significantly higher when compared to bulk materials for any given amount of strain. Further, the new 2D-material-based photodetectors were found to be 1000× more sensitive compared to photodetectors using graphene. Photodetectors capable of such extreme sensitivity could be useful for medical sensing and possibly even quantum information systems, as well as data communication applications.

“Interestingly, unlike bulk materials, two-dimensional materials are particularly promising candidates for strain engineering because they can withstand larger amounts of strain before rupture,” researcher Rishi Maiti said. “In the near future, we want to apply strain dynamically to many other two-dimensional materials in the hopes of finding endless possibilities to optimize photonic devices.”

The research was published in Nature Photonics (www.doi.org/10.1038/s41566-020-0647-4).