Purdue University, the University of Michigan and Pennsylvania State University research team claimed that, has hindered the development of high-performance graphene optics, graphene high-performance optics can be used for imaging, display, sensors and high-speed communications. The paper entitled "Location-Dependent and Millimeter-Range Photodetection of Phototransistors Made of Silicon Carbide Substrates in Combination with Micrometer-scale Graphene" was published in Nature Nanotechnology. The project is jointly funded by the National Science Foundation and the U.S. Department of Homeland Security and is also funded by the National Defense Threat Reduction Agency.

Very thin carbon layer has a unique optical and electronic properties, graphene promising made of high-performance optoelectronic devices. However, the usual graphene photodetectors have only a small area of ​​light sensitive to the beam, limiting their use.

Professor Yong Chen from Purdue University said: "To solve this problem, researchers combined graphene with a relatively large SiC substrate to produce a graphene field-effect transistor that can be activated by light."

High-performance photodetectors can be used for high-speed communications, ultra-sensitive cameras, sensing and wearable electronics. Graphene-based transistor arrays enable high-resolution imaging and display.

Professor Igor Jovanovic, of the University of Michigan in Nuclear Engineering and Radiology said: "Most cameras require a lot of pixels, however our approach makes ultra-sensitive cameras possible, and despite its relatively small number of pixels, the resolution is high."

Professor Jovanovic said: "In a typical graphene photodetector, the photoresponse occurs only at a specific location near graphene, which is much smaller than the device size." However, for many optoelectronic device applications, Large area for light response and position sensitivity. "

New findings show that the device is light sensitive in non-localized areas and is light sensitive even when illuminated on silicon carbide substrates at least 500 μm from graphene. Light response and photocurrent can be increased by almost 10 times, depending on which part of the material is irradiated. In addition, the new phototransistor technology is position-sensitive, so it can determine where light is arriving (important for imaging applications and detectors).

This is the first demonstration of non-localized photodetection using a small piece of graphene on a larger silicon carbide wafer so light does not have to hit the graphene itself. Light can be incident on a larger area, almost a millimeter, and no one has done research before.

Apply voltage between the silicon carbide back and graphene to create an electric field in silicon carbide. Incident light generates photo-carriers in silicon carbide.

The research is concerned with the development of graphene sensors that can be used to detect radiation.

Professor Yong Chen said: "This paper is related to sensors used to detect photons, but the principle is the same as for other types of radiation. We are using sensitive graphene transistors to detect changes in the electric field produced by photons. In this case, light and silicon carbide lining The bottom of the reaction. "

Jovanovic said: "The photodetector can be used for scintillators that detect radiation. Ionizing radiation produces transient light, and photomultiplier tubes (about a century old) in scintillators detect it." Therefore, developing devices that can perform the same function , Advanced devices based on semiconductors are very interesting things. "

In addition, the researchers explained other findings of the computational model. The new transistor was prepared by Purcell Discovery Park's Baker Nano Technology Center.

Future research will include exploring such things as scintillators, astrophysics imaging and high-energy radiation sensors.

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