Temperature-Dependent Opacity of the Gate Field Inside MoS2 Field-Effect Transistors

Le résumé fourni par la source

The transport behaviors of MoS 2 field-effect transistors (FETs) with various channel thicknesses are studied. In a 12 nm thick MoS 2 FET, a typical switching behavior is observed with an I on / I off ratio of 10 6 . However, in 70 nm thick MoS 2 FETs, the gating effect weakens with a large off-current, resulting from the screening of the gate field by the carriers formed through the ionization of S vacancies at 300 K. Hence, when the latter is dual-gated, two independent conductions develop with different threshold voltage ( V TH ) and field-effect mobility (μ FE ) values. When the temperature is lowered for the latter, both the ionization of S vacancies and the gate-field screening reduce, which revives the strong I on / I off ratio and merges the two separate channels into one. Thus, only one each of V TH and μ FE are seen from the thick MoS 2 FET when the temperature is less than 80 K. The change of the number of conduction channels is attributed to the ionization of S vacancies, which leads to a temperature-dependent intra- and interlayer conductance and the attenuation of the electrostatic gate field. The defect-related transport behavior of thick MoS 2 enables us to propose a new device structure that can be further developed to a vertical inverter inside a single MoS 2 flake.

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