Epitaxial graphene quantum dots for high-performance THz bolometers

Light absorption in graphene causes a large change in electron temperature, due to low electronic heat capacity and weak electron phonon coupling [1-3], making it very attractive as a hot-electron bolometer material. Unfortunately, the weak variation of electrical resistance with temperature has substantially limited the responsivity of graphene bolometers. Here we show that quantum dots of epitaxial graphene on SiC exhibit an extraordinarily high variation of resistance with temperature due to quantum confinement, higher than 430 Mohm/K at 2.5 K, leading to responsivities for absorbed THz power above 10^10 V/W. This is five orders of magnitude higher than other types of graphene hot electron bolometers. The high responsivity combined with an extremely low noise-equivalent power, about 0.2 fW/Hz^0.5 at 2.5K, place the performance of graphene quantum dot bolometers well above commercial cooled bolometers. Additionally, these quantum dot bolometers have the potential for superior performance for operation above 77K.