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Graphene Could Yield Cheaper Optical Chips

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Artist's view of the new graphene-on-silicon photodetector.

In a new graphene-on-silicon photodetector, electrodes (gold) are deposited slightly asymmetrically on either side of a silicon waveguide (purple). The asymmetry causes electrons kicked free by incoming light to escape the layer of graphene (hexagons) as

Credit: MIT News

Researchers at the Massachusetts Institute of Technology (MIT), Columbia University, and IBM have developed a new application for graphene in the photodetectors that would convert optical signals to electrical signals in integrated optoelectronic computer chips.

The researchers say that using light instead of electricity to move data within and between computer chips could drastically reduce their power consumption and heat production.

Optoelectronic devices built from graphene also could be much simpler to design than those made from other materials.

"Another advantage, besides the possibility of making device fabrication simpler, is that the high mobility and ultrahigh carrier-saturation velocity of electrons in graphene makes for very fast detectors and modulators," says MIT professor Dirk Englund.

In the new method, light enters the detector through a silicon channel etched into the surface of a chip. The layer of graphene is deposited on top of and perpendicular to the waveguide. On either side of the graphene layer is a gold electrode.

"There's a mismatch between the energy of electrons in the metal contact and in graphene, and this creates an electric field near the electrode," Englund says.

The researchers found that their detector would generate 16 milliamps of current for each watt of incoming light.

From MIT News
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