Enhanced photo-thermoelectric performance of graphene device using modulation of Fermi energy

Abstract

Mono-layer graphene has been studied as an attractive optoelectronic material capable of absorbing light in a wide wavelength range and also providing fast mobility of charge carriers. In recent years, photo-thermoelectric effects of graphene, a thermoelectric voltage due to the temperature distribution of photo-excited and thermalized hot carriers, have been widely studied to generate high photo-response at room temperature. However, Fermi energy change of graphene during the fabrication process causes a problem of low light absorption for a specific wavelength and the Seebeck coefficient, thereby degrading PTE performance. In this study, the graphene PTE device with asymmetric Seebeck coefficient was fabricated, and the Fermi energy of graphene was controlled using chemical and electrostatic methods using ammonia solution and gate voltage. As a result, the enhancement of PTE performance of graphene was confirmed experimentally for appropriate Fermi energy. Also, it was theoretically confirmed that both light absorption, Seebeck coefficient, and the resulting PTE performance of graphene device can be improved through modulation of Fermi energy. This research is expected to be used for a high-performance photo-detector without limitation of the wavelength range.