High Current Density in Monolayer MoS₂ Doped by AlO.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Stable doping is crucial for semiconductor applications like transistors and optoelectronics.
• Doping challenges persist for 2D materials, often leading to instability or processing incompatibility.
• Existing methods for 2D material doping can cause time-dependent hysteresis, hindering device reliability.

Purpose of the Study:

• To develop a stable and process-compatible n-doping method for 2D materials.
• To investigate the use of low-temperature substoichiometric aluminum oxide (AlOx) for doping monolayer molybdenum disulfide (MoS2).
• To assess the performance metrics of MoS2 transistors fabricated with this new doping approach.

Main Methods:

• Fabrication of n-doped monolayer MoS2 using low-temperature (<200°C) substoichiometric AlOx.
• Characterization of carrier density, sheet resistance, and contact resistance in MoS2 transistors.
• Measurement of transistor performance, including current density and on/off ratio, under varying conditions.

Main Results:

• Achieved stable n-doping with carrier densities exceeding 2 × 10^13 cm^-2.
• Demonstrated low sheet resistance (∼7 kΩ/□) and good contact resistance (∼480 Ω·μm).
• Reached record current densities of nearly 700 μA/μm in three-atom-thick MoS2 transistors with an on/off ratio >10^6.

Conclusions:

• Low-temperature substoichiometric AlOx provides a stable n-doping layer for monolayer MoS2, compatible with circuit integration.
• The doped MoS2 devices exhibit high performance, approaching low-power transistor metrics.
• Further improvements in heat sinking could enhance current density beyond 1 mA/μm.