1 research outputs found
Tunable Electron and Hole Injection Enabled by Atomically Thin Tunneling Layer for Improved Contact Resistance and Dual Channel Transport in MoS<sub>2</sub>/WSe<sub>2</sub> van der Waals Heterostructure
Two-dimensional
(2D) material-based heterostructures provide a unique platform where
interactions between stacked 2D layers can enhance the electrical
and opto-electrical properties as well as give rise to interesting
new phenomena. Here, the operation of a van der Waals heterostructure
device comprising of vertically stacked bilayer MoS<sub>2</sub> and
few layered WSe<sub>2</sub> has been demonstrated in which an atomically
thin MoS<sub>2</sub> layer has been employed as a tunneling layer
to the underlying WSe<sub>2</sub> layer. In this way, simultaneous
contacts to both MoS<sub>2</sub> and WSe<sub>2</sub> 2D layers have
been established by forming a direct metal–semiconductor to
MoS<sub>2</sub> and a tunneling-based metal–insulator–semiconductor
contacts to WSe<sub>2</sub>, respectively. The use of MoS<sub>2</sub> as a dielectric tunneling layer results in an improved contact resistance
(80 kΩ μm) for WSe<sub>2</sub> contact, which is attributed
to reduction in the effective Schottky barrier height and is also
confirmed from the temperature-dependent measurement. Furthermore,
this unique contact engineering and type-II band alignment between
MoS<sub>2</sub> and WSe<sub>2</sub> enables a selective and independent
carrier transport across the respective layers. This contact engineered
dual channel heterostructure exhibits an excellent gate control and
both channel current and carrier types can be modulated by the vertical
electric field of the gate electrode, which is also reflected in the
on/off ratio of 10<sup>4</sup> for both electron (MoS<sub>2</sub>)
and hole (WSe<sub>2</sub>) channels. Moreover, the charge transfer
at the heterointerface is studied quantitatively from the shift in
the threshold voltage of the pristine MoS<sub>2</sub> and the heterostructure
device, which agrees with the carrier recombination-induced optical
quenching as observed in the Raman spectra of the pristine and heterostructure
layers. This observation of dual channel ambipolar transport enabled
by the hybrid tunneling contacts and strong interlayer coupling can
be utilized for high-performance opto-electrical devices and applications