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, owing to its optimal channel thickness and improved suppression of extrinsic scattering compared to monolayers. However, its intrinsic phononlimited electron mobility is severely limited by 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 that combines a twist angle near 30∘ with applied stress. Our first-principles calculations demonstrate that although valley separation can be continuously increased using 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 enhanced intravalley scattering induced by phonon softening once the detrimental intervalley scattering is effectively suppressed by sufficient valley separation. This study establishes a theoretical upper limit for the intrinsic electron transport of bilayer MoS₂ masked by severe intervalley scattering.