Electron Excess Doping and Effective Schottky Barrier Reduction on the MoS2/h-BN Heterostructure

Layered hexagonal boron nitride ( h -BN) thin film is a dielectric that surpasses carrier mobility by reducing charge scattering with silicon oxide in diverse electronics formed with graphene and transition metal dichalcogenides. However, the h -BN effect on electron doping concentration and Schottky barrier is little known. Here, we report that use of h -BN thin film as a substrate for monolayer MoS 2 can induce ∼6.5 × 10 11 cm –2 electron doping at room temperature which was determined using theoretical flat band model and interface trap density. The saturated excess electron concentration of MoS 2 on h -BN was found to be ∼5 × 10 13 cm –2 at high temperature and was significantly reduced at low temperature. Further, the inserted h -BN enables us to reduce the Coulombic charge scattering in MoS 2 / h -BN and lower the effective Schottky barrier height by a factor of 3, which gives rise to four times enhanced the field-effect carrier mobility and an emergence of metal–insulator transition at a much lower charge density of ∼1.0 × 10 12 cm –2 ( T = 25 K). The reduced effective Schottky barrier height in MoS 2 / h -BN is attributed to the decreased effective work function of MoS 2 arisen from h -BN induced n -doping and the reduced effective metal work function due to dipole moments originated from fixed charges in SiO 2 .