Junctionless Silicon Nanowire Transistors without the Use of Impurity Doping

Area of Science:

• Semiconductor physics
• Materials science
• Nanotechnology

Background:

• Conventional impurity doping in nanoscale semiconductors faces challenges like statistical variation, temperature sensitivity, and reduced efficiency.
• Carrier freeze-out in highly doped transistors at cryogenic temperatures degrades performance and increases noise.

Purpose of the Study:

• To present an innovative material solution for silicon nanowire junctionless transistors that eliminates the need for impurity doping in the active region.
• To enable stable and efficient operation of transistors at cryogenic temperatures.

Main Methods:

• Fabrication of silicon nanowire junctionless transistors utilizing a SiO2 dielectric shell with engineered defects for direct modulation doping.
• Characterization of nanoscale transport properties, carrier densities, and field-effect mobilities across a wide temperature range (400 K to 77 K).
• Hybrid-density-functional-theory calculations to assess the feasibility for ultrascaled devices.

Main Results:

• Achieved active carrier densities comparable to highly doped devices (~10^18 cm^-3), stable from 400 K down to 77 K.
• Demonstrated enhanced field-effect mobilities (115 to 331 cm^2V^-1s^-1) with decreasing temperature due to the absence of dopants in the channel.
• Obtained high on/off ratios (≥10^6) and stable on-state performance at cryogenic temperatures.

Conclusions:

• Direct modulation doping using defect-engineered SiO2 shells offers a viable alternative to conventional doping for nanoscale transistors.
• The developed device architecture overcomes limitations of impurity doping, enabling energy-efficient cryo-electronics and quantum technologies.
• The method is suitable for ultrascaled device dimensions without fundamental roadblocks.