The strain engineered 2D photodetector could be implemented in applications for medical sensing and quantum computer systems. (Washington University)


Researchers from George Washington University have discovered a new method to engineer optoelectronic devices by extending a 2D material atop a silicon photonic platform. By using this strainoptronics technique, the team has shown that 2D material wrapped around a nanoscale silicon photonic waveguide produces a groundbreaking photodetector that's capable of operating with high efficiency at the critical wavelength of 1550 nm. This type of photodetection can optimize communications and computer systems in growing fields like machine learning and artificial neural networks.


Higher data demand for modern societies often requires data signals in the optical domain to be converted more efficiently, which ranges from fiber optic internet to electronic devices, such as smartphones or laptops. The conversion process from optical to electrical signals are conducted via a photodetector, an important element in optical networks.


2D materials are comprised of scientific and technologically applicable properties. Since they contain strong optical absorption, designing a 2D material-based photodetector allows for an upgraded photo-conversion, which also results in more efficient data transmission and telecommunications. However, there is a downside when using 2D semiconducting materials like the ones from the class of transition metal dichalcogenids: they can't operate with telecommunication wavelengths efficiently since they have a sizeable optical bandgap and low absorption.


Strainoptronics can help overcome this issue by providing an engineering tool for researchers to change the optical and electrical properties of the 2D materials, which will allow 2D material-based photodetectors to be developed for the first time ever.


To create the photodetector, the researchers stretched an extremely thin molybdenum telluride layer atop of a silicon photonic wavelength. Afterward, they modified their physical properties by using their newly developed strainoptronics control knob, which resulted in a lower electronic bandgap. This allowed the device to become operable at near-infrared wavelengths, specifically at the telecommunication (C-band) wavelength near 1550 nm.


The team realized that the 2D semiconductor materials are capable of handling higher amounts of strain compared to bulk materials for a specified amount of strain. The team noted that these 2D material-based photodetectors are 1,000 times more sensitive than other photodetectors that use graphene. These types of photodetectors can be useful data communication applications, medical sensing and potentially quantum computer systems.


"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.' These devices bear unique properties for optical data communication and for emerging photonic artificial neural networks used in machine learning and AI," stated Volker Sorger, associate professor of electrical and computer engineering at GW.


"Interestingly, unlike bulk materials, two-dimensional materials are particularly promising candidates for strain engineering because they can withstand larger amounts of strain before rupture. 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," said Rishi Maiti, postdoctoral fellow in the electrical and computer engineering department at GW.


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