Improvement by Channel Recess of Contact Resistance and Gate Control in Large-Scale Spin-Coated MoS2 MOSFETs

Solution-processed 2-D materials, being low temperature, low cost, and scalable, are attractive for future-generation thin-film and flexible transistors. However, it is challenging to dispense solution-processed 2-D material into a thin and continuous channel for effective and uniform gate control. In addition, a thick channel under the source and drain contacts is required to increase the transfer length and decrease the edge contact resistance. To overcome such a dilemma and to obtain the optimum combination of effective gate control and low contact resistance, channel recess was demonstrated for the first time on MoS
₂
, so that the channel is thin in the gate region but thick in the source and drain regions. Specifically, channel recess by CHF
₃
/O
₂
dry etching up to 60 s was performed on submicron buried-gate MOSFETs fabricated on 20-nm-thick spin-coated MoS
₂
. It was found that the channel recess improved the current on/off ratio by 3 orders of magnitude while maintaining approximately the same contact resistance and peak transconductance as that of a uniformly 20-nm-thick channel. The resulted performance was among the best of all solution-processed MoS
₂
MOSFETs. The same channel recess technique can be used to improve the performance of MOSFETs made of other solution-processed 2-D materials.