Strong Coulomb scattering effects in monolayer WS$_{\mathrm{2}}$ transistor analyzed by low-frequency noise measurement

A monolayer tungsten disulfide (WS$_{\mathrm{2}})$ has recently gained great interests as a new semiconducting material for electronic device due to the controllability of bandgap depending on its thickness, high thermal stability and on/off ratio. In real application, however, those intrinsic properties are easily affected by the extrinsic environmental factors such as substrate doping and surface roughness. Especially, the largely distributed interfacial Coulomb impurities give rise to the severe carrier fluctuation, limiting a signal-to-noise ratio. Here, we report the strong Coulomb scattering effect on low-frequency (LF) noise in monolayer WS$_{\mathrm{2}}$ FETs in respect of temperature [1]. For the better device performance, a nitrogen annealing was carried out. The experimental results are explained well with the carrier number fluctuation and correlated mobility fluctuation model (CNF-CMF), and it is discussed that the electronic transport of WS$_{\mathrm{2}}$ transistor can be strongly dominated by the enhanced Coulomb scattering source located in WS$_{\mathrm{2}}$ channel with carrier trapping/de-trapping processes into the oxide traps. [1] Y. Yun, M. Joo, et al., Appl. Phys. Lett. 109, 153102 (2016)