Origin of Low-Temperature Negative Transconductance in Multilayer MoS2 Transistors
(2021) Applied Physics Letters — p. 10 (2021)
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- Abstract
- In this paper, negative transconductance (NTC) behavior in molybdenum disulfides (MoS2) field effect transistors (FETs) is investigated. Combining experimental observation and numerical analysis, we demonstrate that, positive shift in the device transfer curves results from the electron trapping/de-trapping processes, where the defects densities at the MoS2/SiO2 interface are reduced when the temperature T decreases from 300 to 200 K. Moreover, the main types of defects that affect the device electrical performance are the interface defect and bulk sulfur vacancy VS, in which VS induces the p-type doping effect. While decreasing T below 100 K, NTC occurs when their active layer thickness t (= 41 and 35 nm) is larger than the Debye length λ (28 nm). Considering the n-type doping effect induced by the interface defects and the p-type doping caused by the bulk S vacancies, these two opposite doping regions are carefully implemented into simulation at T = 70 K. A vertical barrier induced by the inhomogeneous electron distribution enlarges with the increased gate bias VGS, and thereafter leads to the unconventional increase of the contact and total resistances with t > λ. While t ≦ λ, the barrier and NTC behavior disappear. The current IDS and transconductance g obtained from the simulation confirm the low-temperature NTC mechanism related to the defects, as discussed above. The material defects and physical origin of NTC discussed in the multilayer MoS2 transistors, provide the theoretical foundation for designing and realizing novel structures of functional devices via defect engineering in the two-dimensional FETs.
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Chen, Q., Li, G., André, N., Liu, X., Xia, Z., Flandre, D., & Liao, L. (2021). Origin of Low-Temperature Negative Transconductance in Multilayer MoS2 Transistors. Applied Physics Letters, 10. https://doi.org/10.1063/5.0058545 (Original work published 2021)