Dual-Gate MoS2FET With a Coplanar-Gate Engineering

Abstract

A dual-gate multilayer MoS2 FET with a standard backside gate and a nonstandard coplanar top gate is demonstrated and analyzed. The special feature of this device is that the gate and MoS2 channel can be directly coupled on the same plane through the bottom-conducting Si substrate. The coplanar-gate MoS2 FET shows a good performance with a large ON–OFF ratio ( $I_{\mathrm{\scriptscriptstyle {ON/OFF}}}$ ) of $1.5\times 10^{4}$ , a small subthreshold swing ( $S$ ) of 0.13 V/decade, and a field-effect mobility ( $\mu $ ) of 0.69 cm2/Vs, respectively. Furthermore, a large $V_{\mathrm {{th}}}$ modulation ( $- 0.55\sim 6.4$ V) can be obtained in a dual-gate MoS2 FET by changing the coplanar-gate bias, which makes the device switch from depletion-mode to enhancement-mode operation, without affecting $\mu $ and $S$ , regardless of the coplanar-gate bias. In such a dual-gate MoS2 FET, both top and bottom gates can share the same SiO2 dielectric, and the deposition of source/drain/gate contact can be combined to a single step. A band diagram with the body effect theory is proposed to explain the device operation mechanism. The coplanar-gate MoS2 FET with its dual-gate operation and simple fabrication process can provide a good candidate for low-cost 2-D planar nanoelectronics and sensor applications.