Hall and field-effect mobilities in few layered p-WSe 2 field-effect transistors

Here, we present a temperature (T) dependent comparison between field-effect and Hall mobilities in field-effect transistors based on few-layered WSe₂ exfoliated onto SiO₂. Without dielectric engineering and beyond a T-dependent threshold gate-voltage, we observe maximum hole mobilities approaching 350 cm² /Vs at T = 300 K. The hole Hall mobility reaches a maximum value of 650 cm² /Vs as T is lowered below ∼150 K, indicating that insofar WSe₂ -based field-effect transistors (FETs) display the largest Hall mobilities among the transition metal dichalcogenides. The gate capacitance, as extracted from the Hall-effect, reveals the presence of spurious charges in the channel, while the two-terminal sheet resistivity displays two-dimensional variable-range hopping behavior, indicating carrier localization induced by disorder at the interface between WSe₂ and SiO₂. We argue that improvements in the fabrication protocols as, for example, the use of a substrate free of dangling bonds are likely to produce WSe₂-based FETs displaying higher room temperature mobilities, i.e. approaching those of p-doped Si, which would make it a suitable candidate for high performance opto-electronics.