NTT Corporation and the National Institute for Materials Science (NIMS) have jointly reported the realization of what they define as "the world's fastest zero-bias operation (220 GHz) of a graphene photodetector (PD)". The research conducted by NTT and NIMS has also, according to the statement, clarified the optical-to-electrical (O-E) conversion process in graphene for the first time.
Graphene is a promising photodetection material for enabling high-speed O-E conversion at wavelength ranges where existing semiconductor devices cannot operate, thanks to its high sensitivity and high-speed electrical response to a wide range of electromagnetic waves, from terahertz (THz) to ultraviolet (UV). However, until now, the demonstrated zero-bias operating speed has been limited to 70 GHz due to conventional device structure and measurement equipment. For this reason, the challenge for graphene PDs is to demonstrate 200-GHz operation speeds and clarify graphene's inherent properties, such the process of optical-to-electrical conversion.