The modulation of Schottky barriers of metal-MoS₂ contacts: Via BN-MoS₂ heterostructures

Using first-principles calculations within density functional theory, we systematically studied the effect of BN-MoS₂ heterostructure on the Schottky barriers of metal-MoS₂ contacts. Two types of FETs are designed according to the area of the BN-MoS₂ heterostructure. Results show that the vertical and lateral Schottky barriers in all the studied contacts, irrespective of the work function of the metal, are significantly reduced or even vanish when the BN-MoS₂ heterostructure substitutes the monolayer MoS₂. Only the n-type lateral Schottky barrier of Au/BN-MoS₂ contact relates to the area of the BN-MoS₂ heterostructure. Notably, the Pt-MoS₂ contact with n-type character is transformed into a p-type contact upon substituting the monolayer MoS₂ by a BN-MoS₂ heterostructure. These changes of the contact natures are ascribed to the variation of Fermi level pinning, work function and charge distribution. Analysis demonstrates that the Fermi level pinning effects are significantly weakened for metal/BN-MoS₂ contacts because no gap states dominated by MoS₂ are formed, in contrast to those of metal-MoS₂ contacts. Although additional BN layers reduce the interlayer interaction and the work function of the metal, the Schottky barriers of metal/BN-MoS₂ contacts still do not obey the Schottky-Mott rule. Moreover, different from metal-MoS₂ contacts, the charges transfer from electrodes to the monolayer MoS₂, resulting in an increment of the work function of these metals in metal/BN-MoS₂ contacts. These findings may prove to be instrumental in the future design of new MoS₂-based FETs with ohmic contact or p-type character.