  We propose to utilize multiple-graphene-layer structures with lateral p-i-n
junctions for terahertz (THz) and infrared (IR) photodetection and substantiate
the operation of photodetectors based on these structures. Using the developed
device model, we calculate the detector dc responsivity and detectivity as
functions of the number of graphene layers and geometrical parameters and show
that the dc responsivity and detectivity can be fairly large, particularly, at
the lower end of the THz range at room temperatures. Due to relatively high
quantum efficiency and low thermogeneration rate, the photodetectors under
consideration can substantially surpass other THz and IR detectors.
Calculations of the detector responsivity as a function of modulation frequency
of THz and IR radiation demonstrate that the proposed photodetectors are very
fast and can operate at the modulation frequency of several tens of GHz.
