Abstract
Photodetectors and display backplane transistors based on molybdenum disulfide (MoS2) have been regarded as promising topics. However, most studies have focused on the improvement in the performances of the MoS2 photodetector itself or emerging applications. In this study, to suggest a better insight into the photodetector performances of MoS2 thin film transistors (TFTs), as photosensors for possible integrated system, we performed a comparative study on the photoresponse of MoS2 and hydrogenated amorphous silicon (a-Si:H) TFTs. As a result, in the various wavelengths and optical power ranges, MoS2 TFTs exhibit 2~4 orders larger photo responsivities and detectivities. The overall quantitative comparison of photoresponse in single device and inverters confirms a much better performance by the MoS2 photodetectors. Furthermore, as a strategy to improve the field effect mobility and photoresponse of the MoS2 TFTs, molecular doping via poly-L-lysine (PLL) treatment was applied to the MoS2 TFTs. Transfer and output characteristics of the MoS2 TFTs clearly show improved photocurrent generation under a wide range of illuminations (740~365 nm). These results provide useful insights for considering MoS2 as a next-generation photodetector in flat panel displays and makes it more attractive due to the fact of its potential as a high-performance photodetector enabled by a novel doping technique.
Highlights
Published: 17 June 2021For achieving the ultimate scaling of Si devices below a sub-nanometer, direct tunneling of leakage current in the channel is a critical problem to be resolved, because it can lead to large power consumption [1,2]
The extracted electrical properties indicate that the quality of fabricated thin film transistors (TFTs) was reasonable compared with previous results in the literature [31,37,38,39]; the photoresponse of both TFTs were ready to be compared without consideration of noticeable defects or flaws
The photosensitive m-MoS2 depletion load enhancement driver (DLED) inverter showed robust advantages with regard to level of device integration per area, chip density, and sensitive modulation properties in variations of wavelength from dark to blue as compared to an amorphous silicon (a-Si):H DLED inverter
Summary
For achieving the ultimate scaling of Si devices below a sub-nanometer, direct tunneling of leakage current in the channel is a critical problem to be resolved, because it can lead to large power consumption [1,2]. TFTs, which are presently one of the most promising display backplane TFTs with high mobility and maturity of material, MoS2 TFTs possess advantages of detecting spectrum and negligible photo persistent current (PPC) effects [31,32] This comparative study was expected to provide intuitive criteria for researchers in terms of the key aspects that are required for MoS2 layers as one of the next-generation semiconductors for the future photodetectors in display systems. Various doping methods have been applied including high-k-based fixed-charge induction, moleculeinduced charge transfer, organic solvents-based doping, electrical doping via local electrode configuration, electrothermal doping, and gas-based doping Among these techniques, molecular doping has been predominantly utilized owing to the immediately accessible approach with several advantages such as post process compatibility, unnecessity to deposit additional layers, and low temperature during the treatment on devices. These results will provide useful insights for considering MoS2 as a next-generation photodetector in flat panel displays and make it more attractive as a potential highperformance photodetector enabled by a novel doping technique
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