Physicists from the Moscow Institute of Physics and Technology with colleagues from the Moscow State Pedagogical University and the University of Manchester have created a highly sensitive terahertz radiation detector based on the tunneling effect in graphene. In fact, a field tunnel transistor was turned into a detector, which could be opened by signals “out of thin air”, and not transmitted through conventional circuits.
quantum tunneling. Image source: Daria Sokol, MIPT press service
The discovery made, which was based on the ideas of the physicists Mikhail Dyakonov and Mikhail Shur proposed back in the early 1990s, brings the era of wireless terahertz technologies closer. This means that the speed of wireless communication will increase many times, and radar technologies and technologies for security systems, radio astronomy and medical diagnostics will rise to a qualitatively new level.
The idea of Russian physicists was that the tunnel transistor was proposed to be used not for signal amplification and demodulation, but as a device that "by itself turns a modulated signal into a sequence of bits or voice information due to the non-linear relationship between current and voltage." In other words, the tunneling effect can occur at an extremely low signal level at the gate of the transistor, which will allow the transistor to initiate tunneling current (open) even from a very weak signal.
Why is the classic transistor scheme not suitable? When switching to the terahertz range, most of the existing transistors do not have time to get the required charge, so the classic radio circuit with a weak signal amplifier on a transistor with subsequent demodulation becomes inefficient. It is necessary either to improve transistors, which also works up to a certain limit, or to offer something completely different. Russian physicists just proposed this “other”.
Graphene tunnel transistor as a terahertz detector. Image Source: Nature Communications
“The idea of a strong response of a tunnel transistor to low voltages has been known for about fifteen years,” says Dmitry Svintsov, one of the authors of the study, head of the laboratory for optoelectronics of two-dimensional materials at the Center for Photonics and Two-Dimensional Materials of the Moscow Institute of Physics and Technology. “Before us, no one realized that the same property of the tunnel transistor can be applied in the technology of terahertz detectors.” As scientists have established, “if a transistor opens and closes well at a low power of the control signal, then it should also pick up a weak signal from the air well.”
For the experiment, which is described in the journal Nature Communications, a tunnel transistor was created on two-layer graphene. The experiment showed that the sensitivity of the device in the tunnel mode is several orders of magnitude higher than that in the classical transport mode. Thus, the experimental transistor-detector turned out to be no worse in sensitivity than similar superconducting and semiconductor bolometers available on the market. The theory suggests that the purer the graphene, the higher the sensitivity will be, which far exceeds the capabilities of modern terahertz detectors, and this is no longer an evolution, but a revolution in the industry.
Source: 3dnews.ru