  This article reviews recent research for development of sensitive graphene
photon detectors in the infrared/far infrared/THz range. For this range,
graphene has promising potential in thermal photon detectors. Graphene has
ultra-small volume and low electron density, which gives relatively large
heating per absorbed photon and fast response. At low temperatures the
electron-phonon energy loss is small, so ultrasensitive power detection is
possible. We review recent research on the science base of such detectors, and
outline the major design challenges. Important factors that must be considered
in making useful detectors include the photon and readout coupling efficiency,
the method of electron temperature readout, and thermal isolation of the hot
electrons.
