Carrier Polarity Control in α-MoTe₂ Schottky Junctions Based on Weak Fermi-Level Pinning

The polarity of the charge carriers injected through Schottky junctions of α-phase molybdenum ditelluride (α-MoTe₂) and various metals was characterized. We found that the Fermi-level pinning in the metal/α-MoTe₂ Schottky junction is so weak that the polarity of the carriers (electron or hole) injected from the junction can be controlled by the work function of the metals, in contrast to other transition metal dichalcogenides such as MoS₂. From the estimation of the Schottky barrier heights, we obtained p-type carrier (hole) injection from a Pt/α-MoTe₂ junction with a Schottky barrier height of 40 meV at the valence band edge. n-Type carrier (electron) injection from Ti/α-MoTe₂ and Ni/α-MoTe₂ junctions was also observed with Schottky barrier heights of 50 and 100 meV, respectively, at the conduction band edge. In addition, enhanced ambipolarity was demonstrated in a Pt-Ti hybrid contact with a unique structure specially designed for polarity-reversible transistors, in which Pt and Ti electrodes were placed in parallel for injecting both electrons and holes.