Enhancing Carrier Mobility in Monolayer MoS₂ Transistors with Process-Induced Strain

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) electronic materials offer potential for next-generation electronics due to excellent size scaling.
• Integrating 2D materials with existing CMOS processes is challenging, with limited understanding of how processing affects material properties.
• Strain and doping significantly impact 2D material device performance, but their interplay with fabrication steps is not well understood.

Purpose of the Study:

• To investigate the impact of process-induced strain on the electronic properties of 2D material transistors.
• To demonstrate the use of a common semiconductor industry technique, thin film deposition, to tune strain in 2D materials.
• To correlate changes in strain and doping with device performance in monolayer MoS2 transistors.

Main Methods:

• Systematic variation of tensile strain in monolayer MoS2 transistors using iterative deposition of MgO stressor layers.
• Combined Raman spectroscopy and electrical transport measurements to analyze strain, doping, and device characteristics.
• Characterization of strain uniformity and mechanical stability at different stressor thicknesses.

Main Results:

• Achieved uniform tensile strain up to 0.48 ± 0.05% in MoS2 channels with 150 nm MgO stressors.
• Observed mechanical instability and nonuniform strain at higher stressor thicknesses.
• Demonstrated a significant enhancement in electron mobility (130 ± 40% per % strain) and channel saturation current density (52 ± 20%) with increasing tensile strain.

Conclusions:

• Process-induced strain is an effective method to enhance carrier mobility and current density in 2D transistors.
• Established CMOS fabrication techniques can be adapted to precisely control strain in 2D materials.
• This approach accelerates the integration of 2D electronics into future computing architectures by leveraging existing industry processes.