Dual-Gate MoS2 FET With a Coplanar-Gate Engineering

A dual-gate multilayer MoS
₂
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 MoS
₂
channel can be directly coupled on the same plane through the bottom-conducting Si substrate. The coplanar-gate MoS
₂
FET shows a good performance with a large ON-OFF ratio (ION/OFF) of 1.5 × 104, a small subthreshold swing (S) of 0.13 V/decade, and a field-effect mobility (μ) of 0.69 cm
²
/Vs, respectively. Furthermore, a large Vth modulation (-0.55~6.4 V) can be obtained in a dual-gate MoS
₂
FET by changing the coplanar-gate bias, which makes the device switch from depletion-mode to enhancement-mode operation, without affecting μ and S, regardless of the coplanar-gate bias. In such a dual-gate MoS
₂
FET, both top and bottom gates can share the same SiO
₂
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 MoS
₂
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.