  Semiconducting MoTe2 is one of the few two-dimensional (2D) materials with a
moderate band gap, similar to silicon. However, this material remains
under-explored for 2D electronics due to ambient instability and predominantly
p-type Fermi level pinning at contacts. Here, we demonstrate unipolar n-type
MoTe2 transistors with the highest performance to date, including high
saturation current (>400 ${\mu}A/{\mu}m$ at 80 K and >200 ${\mu}A/{\mu}m$ at
300 K) and relatively low contact resistance (1.2 to 2 $k{\Omega}\cdot{\mu}m$
from 80 to 300 K), achieved with Ag contacts and AlOx encapsulation. We also
investigate other contact metals, extracting their Schottky barrier heights
using an analytic subthreshold model. High-resolution X-ray photoelectron
spectroscopy reveals that interfacial metal-Te compounds dominate the contact
resistance. Among the metals studied, Sc has the lowest work function but is
the most reactive, which we counter by inserting monolayer h-BN between MoTe2
and Sc. These metal-insulator-semiconductor (MIS) contacts partly de-pin the
metal Fermi level and lead to the smallest Schottky barrier for electron
injection. Overall, this work improves our understanding of n-type contacts to
2D materials, an important advance for low-power electronics.
