High-Gain Phototransistors Based on a CVD MoS_2 Monolayer

摘要

Graphene, one of the most promising two-dimensional materials, has great potential in various applications, including nanoelectronics, optoelectronics, energy harvesting, and bio-sensing. The linear dispersion of the Dirac electrons makes graphene-based broadband optical modulators and ultrafast high frequency photodetectors possible. However, the zero bandgap of graphene limits its applications in nanoelectronics and optoelectronics. With this consideration, the molybdenum disulfide (MoS_2) monolayer recently emerged with a direct bandgap of 1.8 eV. The large direct bandgap, high electron mobility (≈200 cm~2 V~(-1) s~(-1)), excellent current ON/OFF ratio (≈10~8), low subthreshold swing (≈74 mV dec~(-1)), and high quantum luminescence efficiency of monolayered MoS_2 make it a new hot research topic, especially in the field of optoelectronics.A phototransistor made from a monolayer of MoS_2 has shown a high photoresponsivity (≈7.5 mA W~(-1)) and a short response time (≈50 ms). Also, the wavelength dependent photosensitivity varies with the thickness of MoS_2. Moreover, the phototransistors based on multilayers of MoS_2 exhibit a broad spectral response from ultraviolet to infrared. All these properties indicate that the MoS_2 layers are promising as new building blocks for optoelectronic devices.