Thickness-Dependent Schottky Barrier Height of MoS2 Field-Effect Transistors
2D semiconductors including transition metal dichalcogenides(TMDs) have been widely studied recently because of their excellent electrical properties for channel materials of transistors, optoelectronic devices like light emitting diodes, photodetectors and solar cells while graphene is difficult to be used due to its zero bandgap. Especially, researches on MoS2, the representative TMD material, have shown a great potential as a candidate for the next generation electronics with excellent carrier mobility and subthreshold swing. However, device performance is deteriorated due to the significant contact resistance observed at interface between MoS2 and metal electrode. Contact resistance of MoS2-metal contacts decreases with the thickness of MoS2. It is mainly due to the layer-dependent band gap of MoS2. In this work, aluminum which has a low work function is utilized as contact electrodes to minimize Schottky barrier with n-type MoS2. Thickness-dependent contact resistances of various MoS2 devices were obtained for analysis of the effects of band alignment change on the contact resistance. We obtained contact resistance as low as about 70meV when MoS2 is trilayer-thick. It is important to find optimal choice of contact metal and layer thickness of MoS2 for high performance electronic devices which have low contact resistances.