Hot Carriers in CVD-Grown Graphene Device with a Top h-BN Layer

Abstract

We investigate the energy relaxation of hot carriers in a CVD-grown graphene device with a top h-BN layer by driving the devices into the nonequilibrium regime. By using the magnetic field dependent conductance fluctuations of our graphene device as a self-thermometer, we can determine the effective carrier temperature e at various driving currents while keeping the lattice temperature L fixed. Interestingly, it is found that e is proportional to I, indicating little electron-phonon scattering in our device. Furthermore the average rate of energy loss per carrier e is proportional to ( e 2 − L 2 ), suggesting the heat diffusion rather than acoustic phonon processes in our system. The long energy relaxation times due to the weak electron-phonon coupling in CVD graphene capped with h-BN layer as well as in exfoliated multilayer graphene can find applications in hot carrier graphene-based devices.