Junctionless Silicon Nanowire Transistors without the Use of Impurity Doping

TL;DR

This paper introduces a new type of silicon nanowire transistor that doesn't require traditional doping, offering better performance at low temperatures.

Contribution

The paper presents a novel doping-free method using defect-engineered SiO2 shells to create junctionless transistors with high performance at cryogenic temperatures.

Findings

The transistors achieve carrier densities comparable to highly doped devices (∼10¹⁸ cm⁻³) across a wide temperature range.

Field-effect mobilities increase significantly at lower temperatures, from 115 to 331 cm²/V·s.

The devices maintain a high on/off ratio (≥10⁶) and stable performance down to 77 K.

Abstract

With
the shrinking dimensions of semiconductor structures reaching
the nanoscale, conventional impurity doping techniques face several
challenges due to their statistical nature, temperature dependence,
and degradation in efficiency of the doping method. In addition, the
cryogenic operation of highly doped transistors is complicated due
to carrier freeze-out, which significantly reduces the availability
of mobile charges, degrading device performance and inducing noise.
Here, an innovative material solution is presented that enables silicon
nanowire junctionless transistors without requiring impurity doping
within the active semiconductor region. To this end, a SiO2 dielectric shell with deliberate defect engineering surrounding
both the channel and the contact regions - known as direct modulation
dopingis used to modify the nanoscale transport properties
of the silicon. The obtained active carrier densities in the experiment
are comparable to highly impurity-doped devices in the range of
∼1018⁡cm−3
and remain stable over a broad temperature
range from 400 K down to 77 K. The primary advantage of removing dopants
from the channel is evident in the enhanced field-effect mobilities,
which increase from 115 to 331 cm2V–1s–1 as temperature decreases. The fabricated nanowire
transistors in this work provide a high on/off ratio of ≥106, and a stable on-state performance down to 77 K. Hybrid-density-functional-theory
calculations are carried out to show that there are no fundamental
roadblocks to employing the method to devices with ultrascaled dimensions.
The device architecture is positioned for applications in energy-efficient
cryo-electronics and quantum technologies by addressing the limitations
associated with conventional impurity doping.

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