Graphene to Be Used for Next-Gen Photodetectors

Since it was first discovered in the United Kingdom, back in 2004, the carbon compound graphene has been used for a wide variety of applications, from creating amazingly fast transistors to producing very dense memory chips. Now, with research in these areas well underway, physicists are beginning to explore its uses in optoelectronics, especially in the field of detecting photons. Researchers at IBM believe that graphene has the natural ability of making an excellent photodetector, and have started work on exploring this possibility, Technology Review reports.

Usually, III-V semiconductors are used for producing this type of detectors. They include several chemicals, most commonly gallium and phosphorus, and can be a pain to manufacture. Their operating principle is fairly basic – light hitting them produces an electron-hole in the materials, and these electrons are then channeled out of the material, and transformed into electrical impulses. According to the IBM team, the one-atom-thick structure of graphene can transport these signals tens of times faster than III-V semiconductors, which would result in faster and more efficient photodetectors.

Additionally, graphene is also able to absorb infrared wavelengths, whereas regular detectors can only make out a narrow range from the near-infrared spectrum. The thing about graphene is that the absorbed photons – which generate the electron-holes – undergo their reactions at the picosecond scale. This means that the electrons and the holes combine extremely fast, and leave no spare, free electrons for producing electrical signals. “If we can have some kind of an electric field to separate the electron-hole pairs, we can collect them fast enough [for current],” IBM's T. J. Watson Research Center Manager for Nanometer Scale Science and Technology Phaedon Avouris explains.

The team estimates that graphene can absorb as much as 2.3 percent of the light falling over it, which is an extremely high percentage for a material just one atom thick. “You have a photodetector that has a number of advantages: it absorbs over a wide wavelength range, it's very fast, it has a high absorbance, it's a single atomic layer. This combination makes it rather unique,” Avouris adds. “Graphene is a great material for electronics. Very few people could think about optoelectronics being of any interest with this material. This is like fresh air,” University of Manchester Professor of Physics Andre Geim concludes. He was the leader of the team that discovered graphene.