Approaching the Intrinsic Electron Mobility Limit of Bilayer MoS₂ via a Combined Twist-Angle and Stress-Engineering Strategy

Bilayer MoS₂ is a promising channel candidate for extending Moore’s law due to its optimal channel thickness and enhanced suppression of extrinsic scattering compared to monolayers. However, its intrinsic phonon-limited electron mobility is severely restricted by the enhanced K-Q intervalley scattering arising from the multivalley conduction band feature inherent to the bilayer structure. To overcome this bottleneck, we propose a “valley separation engineering” strategy, combining a twist angle near 30∘ with applied stress. Our first-principles calculations demonstrate that although the valley separation can be continuously increased via this strategy, the electron mobility saturates at ~200 cm² V^-1 s^-1. The saturation is attributed to the competition between the reduced effective mass and the enhanced intravalley scattering induced by phonon softening, once the detrimental intervalley scattering is effectively suppressed by sufficient valley separation. This work establishes a theoretical upper limit for the intrinsic electron transport of bilayer MoS₂ masked by severe intervalley scattering.