Temperature-Dependent RF Characteristics of Al₂O₃-Passivated WSe₂ MOSFETs

Of all two-dimensional semiconductor crystals, WSe
₂
is particularly interesting due to its sizable bandgap, high carrier mobility, and compatibility with large-scale synthesis. By passivating WSe2 MOSFETs with atomic-layer-deposited Al
₂
O
₃
, they are stable in room environment for more than five months. The passivation also increases their current capacity by two orders of magnitude. Their cutoff frequencies peak around room temperature, with the forward current cutoff frequency f
_T
~ 0.6 GHz and the maximum frequency of oscillation f
_MAX
~ 2 GHz. These results show WSe
₂
is a promising material for gigahertz thin-film transistors. However, if the surface passivation is not optimized, fixed charge in the passivation layer may lead to temporal and temperature instabilities.