Photocurrent Measurement of Multiple Top Gated Graphene Devices

Inefficient electron-phonon relaxation in graphene results in long-lived hot carriers that proliferate over large spatial scales, associated with long-range energy and momentum transport. In order to investigate the propagation length of hot carriers, we report on photocurrent measurements using graphene devices with a global back-gate and multiple local top-gates. The purpose of the latter is to facilitate independent modulation of the Seebeck coefficient at different distances from the position of laser illumination. By varying the voltages of the top gates separately and measuring the change in photovoltage, we investigate the electronic temperature gradient at each gate through the Seebeck effect.