NTT implemented the world fastest zero bias operation of the graphene light sensor photodevice in collaboration with national research-and-development corporation National Institute for Materials Science (NIMS). Furthermore, they solved optical electricity translation process in the graphene.

A light sensor photodevice is a device which changes optical signal into electrical signal and detects light electrically.

The graphene is expected to carry out an electric response to the high sensitivity and the high-speed to the light of the wideband from terahertz wave to ultraviolet light. This is a favorable material which high-speed optical-electricity translation is attained in the wavelength universe which the existing semiconductor device does not operate.

However, the actual proof operating speed under zero bias was restricted to 70GHz on the problem of device architecture or measurement equipment.

In this Research, they removed the electric-current latency originating in device architecture. And they succeeded in proving the operating speed of 220 GHz by reading an electric current at high speed using on-chip terahertz part opto-electronics.