Point Defect Limited Carrier Mobility in 2D Transition Metal Dichalcogenides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Semiconductor Physics

Background:

• Two-dimensional transition metal dichalcogenides (2D MX2) are vital for electronics and optoelectronics.
• Their practical application is limited by low room-temperature charge carrier mobility.
• Defects are known scattering sources, but their precise impact on mobility is not fully quantified.

Purpose of the Study:

• To quantitatively assess the impact of various defects on carrier mobility in 2D MX2 semiconductors.
• To elucidate the underlying mechanisms for mobility differences between MoX2 and WX2.
• To provide guidelines for experimental defect engineering to optimize device performance.

Main Methods:

• Utilized first-principles calculations to model defect scattering mechanisms.
• Calculated carrier mobilities for various MX2 materials (M = Mo/W, X = S/Se) with different defect types.
• Analyzed electron-defect coupling strengths to explain observed mobility trends.

Main Results:

• Tungsten-based (W) MX2 consistently exhibited higher mobility than Molybdenum-based (Mo) MX2, irrespective of defect type or carrier.
• Weaker electron-defect coupling in WX2 was identified as the primary reason for superior mobility.
• Oxygen substitution in chalcogen vacancies improved mobility, while metal atom substitution generally decreased it (except for WSe2).

Conclusions:

• Defect type and composition significantly influence carrier mobility in 2D MX2.
• Tungsten-based materials offer inherent advantages for high-mobility applications.
• Identifying critical defect concentrations is crucial for maximizing mobility and achieving optimal device performance.