High-responsivity molybdenum diselenide photodetector with dirac electrodes

Abstract

Two-dimensional molybdenum diselenide (MoSe2) has attracted immense attention in the field of next-generation optoelectronic devices for its unique structure and excellent photosensitivity. However, the Schottky barrier and surface defects at the interface between the electrode and MoSe2 channel limit the performance of MoSe2 photodetectors. Here, using Dirac graphene electrodes, a high performance MoSe2 photoconductive photodetector was fabricated via mechanical exfoliation. In contrast with photodetectors using Mo/Au electrodes with a high Schottky barrier of 196.7 meV, the devices using graphene electrodes maintain linear ohmic contacts owing to the alignment of the work function and Fermi-level depinning, thereby resulting in fast transient response time on the order of 30 ms and high responsivity exceeding 103 A/W. Moreover, we simultaneously demonstrate the effects of contact resistance on responsivity, response time, and light–dark current ratio of MoSe2 photodetectors. Further, the hysteresis accompanying the adsorption and desorption of water and oxygen molecules in ambient air was eliminated owing to a high photocurrent level between source and drain. This research unveils the vast potential of proper electrode contact selection to further improve the performance of photodetectors.