MIPT Scientists Design Graphene Heterostructures to Develop New Infrared Detectors

The findings, which saw the team from MIPT collaborating with scientists in Japan and the US, showed that the new sensors were able to detect radiation with energy less than the bandgap of the constituent layers without graphene.

The new devices would also be easier to modify than infrared sensors, allowing for increased sensitivity adjustable to the required wavelength of light. The research was published in the journal Optics Express and paves the way for the manufacturing of sensors capable of replacing far-infrared and terahertz radiation detectors.

 

Beyond 1.55 μm

Graphene has been widely utilized in the development of high-speed photodetection for silicon photonics over a wide wavelength range.

The high conductivity of this material changes when molecules in a given environment interact and this measurable change is one of the most common sensing mechanisms upon which many sensors are built. However, even the fastest graphene photodetectors operate in the 1.55 μm wavelength band.

Using an ultrathin wide silicon−graphene hybrid plasmonic waveguide, the MIPT team was now able to enable efficient light absorption in graphene at 1.55 μm and beyond.

To achieve these results, the researchers surrounded the graphene layer with layers made of black phosphorus and black arsenic in varying proportions. By modifying the ratio of these substances, the working range of the photodetector shifted.

 

Promising Results for Sensors 

In other words, the way the detector works is by registering an electron or hole entering the conduction band of black phosphorus or arsenic following a transition between two energy bands of graphene.

The results of these experiments were very promising. While operating at 2 μm, for example, the new photodetector showed a responsivity of ~70 mA/W and a setup-limited 3 dB bandwidth of >20 GHz.

When operating at 1.55 μm, the device showed solid results with a 3 dB bandwidth of >40 GHz (setup-limited) and high responsivity of ~0.4 A/W even with a low bias voltage of −0.3 V. 

“By applying a carefully calibrated voltage, the working range of the detectors can be changed without affecting signal reception quality,” said Victor Ryzhii, the head of the 2-D Materials and Nanodevices Laboratory. “Such sensors could enhance the performance of infrared telescopes.”

 

 

A graphical representation of the layers structures tested on by MIPT researchers. Image used courtesy of Daria Sokol/MIPT.

 

Replacing Infrared Sensors?

According to Ryzhii, the team’s calculations showed that at high temperatures the detectors will produce a much cleaner signal than the detectors used now. On account of these capabilities, the new devices may benefit many areas of science and technology, both in household applications and for fundamental science.

 

Utilizing Infrared Sensors to Improve Applications 

In fact, infrared light sensors are currently utilized in a variety of devices, including heartbeat sensors, night vision equipment, remote controls, and autonomous vehicles.

The new research could improve applications related to all the above devices, as well as being used to design airport scanners not utilizing X-ray technology, which radiation is potentially harmful to the human body (the radiation emitted by said scanners is minimal, however). 

“Such devices can replace almost any far-infrared and terahertz radiation sensors used today,” Ryzhii explained. “The decreased dark current and the high photosensitivity significantly improve the signal-to-noise ratio even for low-intensity radiation. ”