Mobility Enhancement of Monolayer MoS2 Transistors using Tensile-Stressed Silicon Nitride Capping Layers

Strain engineering has played an important role in modern transistor technology, improving mobility in Si devices since the 90 nm node. Tensile silicon nitride (SiN
x
) capping layers for Si NMOS have been an effective way to enhance mobility by modifying the Si band structure [1]. 2D semiconductors such as mono-layer (IL) MoS
2
are also predicted to have improved mobility under tensile strain, by reduction of intervalley scattering and effective mass [2]. However, CMOS-compatible strain techniques have yet to be demonstrated for such 2D semiconductors. Here, we demonstrate improvement in the mobility and on-state current of 1L MoS
2
transistors using a high-tensile-stress SiN
x
capping layer. We achieve up to 47% improvement in back-gated FET (BG-FET) mobility and on-state current, then extend the technique to achieve 33% improved current drive in top-gated FETs (TG-FET), with record saturation current up to 488 µA/µm in a 200 nm long channel.