Electrical Measurement of the Band Gap of Molybdenum Ditelluride and Black Phosphorus in Ambipolar Transistors with Graphene Source/Drain Contact

Abstract

Transition metal dichalcogenides and monoatomic buckled crystals are two-dimensional (2D) semiconductors promising for active material toward nano-electronics and nano-optoelectronics [1]. As some of recent 2D semiconductors, α-MoTe2 and black phosphorus(BP) have been extensively studied due to their optical and electrial propeties. Many groups have theoretically predictd band gap of α-MoTe2 and black phosphorus in a wide range [2], depending on their film thickness. However, only a few experimental measurements have been done. Here, we demonstrate ambipolar α-MoTe2 and black phosphorus transistors with graphene source and drain contacts to determine the band gap of channel. Temperature-dependent transfer characteristics have been used to quantitatively analyze schottky barriers height(ФB) formed at the graphene-to-channel interface as a function of applied gate voltage. Because Fermi level of graphene is modulated to that of channel, we can determine band gap of 11 nm-thin α-MoTe2 and 6 nm-thin black phosphorus are 0.826 eV and 0.416 eV, respectively. Our estimated band gap values appear quite reasonable, proving that our analysis is very useful to estimate the band gap of 2D material. Figure 1