ReS₂ Nanosheet-Based Channels for Two-Dimensional Field Effect Transistors and Phototransistors with High Photoresponsivity

Compared to traditional bulk materials, two-dimensional transition metal dichalcogenides (2D TMDCs) hold the potential in low power logic, photoelectric, and nonvolatile memory devices due to a tunable band structure, pure heterojunction interface, and photodetection for a wide spectral range. ReS₂ is chosen as the channel material in our work because it possesses excellent photoresponsivity. In addition, a BN dielectric is inserted between SiO₂ and ReS₂ as a gate dielectric. The pure heterojunction interface at BN/ReS₂ enhances the electric characteristics, including negligible hysteresis window and higher mobility. The photoelectric measurement results show that ReS₂ devices with or without the BN dielectric have an outstanding photoresponsivity of up to ∼10⁶ A/W and a specific detectivity of up to ∼10¹³ Jones as well as a fast photoresponse time of less than 100 ms under an extremely low optical power density of 0.47 μW/cm², which fully proves that ReS₂ has the ability to detect very weak light. Also, the contact resistance and Schottky barrier height are also extracted with variable temperature measurements for the ReS₂ device. The higher contact resistance and unsymmetric output currents illustrate that the mirror force is the main factor leading to the reduction of the Schottky barrier height. Finally, the influences of the ReS₂ channel thickness on mobility and photoresponsivity are also studied by the device-to-device variability. The work in this paper further demonstrates that nanosheet-based ReS₂ can be regarded as an excellent candidate for application into the field of light-sensitive sensors under the condition of the CMOS-compatible process.