Understanding the electric field dependent channel migration for shorter channel length of multilayer rhenium disulfide (ReS₂) FETs

초록

Multilayer rhenium disulfide (ReS2) has attracted considerable attention due to the decoupled van der Waals interaction between its adjacent layers, leading to significantly higher interlayer resistance compared with other layered materials. While the carrier transport in multilayer materials can be well described by the interlayer resistance (RInt) and Thomas-Fermi charge screening length ( lambda TF) in resistor network models, the electric field scaling of the channel with the back gate voltage (VBG) and the drain voltage (VD) is limited in two-dimensional (2D) multilayer materials. In this report, we present the effects of VBG and VD on the channel migration of ReS2 field effect transistors (FETs) with channel lengths of 0.25, 2.4, and 4.4 mu m. For shorter channels, the VBG-dependent conductance (G = (drain current (ID)/VD)) increases with increasing VD, different from the longer channels. Based on the resistor network model, the different behaviors with channel lengths were analyzed by considering the interlayer resistance (RInt) versus the channel resistance and the Thomas-Fermi charge screening length ( lambda TF). Lower back gate voltage (VBG) in shorter channels builds the channel near the bottom layer close to the oxide, while high VBG shifts the conductive channel to the top sheet exposed to ambient condition. In longer channels, due to the increased channel resistance (Rch), the conductive channel forms near the bottom side close to the oxide. The increase of the threshold voltage (Vth) was observed at higher drain-source voltages (VD), but in opposite for the top side channel, i.e. the decrease of threshold voltage with increasing VD. This study will give a hint on establishing the electric field scaling of 2D material-based FETs with channel lengths and applied voltages of VBG and VD.

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