Back-Gate GaN Nanowire-Based FET Device for Enhancing Gas Selectivity at Room Temperature

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Metal oxide gas sensors, like titanium dioxide (TiO2), exhibit high sensitivity but suffer from cross-sensitivity issues, particularly distinguishing between nitrogen dioxide (NO2) and sulfur dioxide (SO2).
• Existing two-terminal TiO2/GaN chemiresistors show promise for NO2 detection but lack selectivity.

Purpose of the Study:

• To design and implement a TiO2-coated GaN nanowire-based back-gate field-effect transistor (FET) device.
• To enhance the selectivity of gas sensors for NO2 and SO2 detection at room temperature using a tunable back-gate bias.

Main Methods:

• Fabrication of a TiO2-coated GaN nanowire FET device incorporating a silicon (Si) back gate with Carbon-Aluminum Gallium Nitride (C-AlGaN) as the gate dielectric.
• Application of back-gate bias to modulate the sensor's response to NO2 and SO2 at room temperature (20 °C).
• Utilized density functional theory (DFT) to model molecular energetics and derive band diagrams for explaining gas response variations.

Main Results:

• A significant 60% increase in NO2 response was observed with back-gate bias compared to no bias.
• An insignificant 10% increase in SO2 response was noted under the same back-gate bias conditions.
• The back-gate bias effectively enhanced the discrimination between NO2 and SO2, demonstrating improved selectivity.

Conclusions:

• The developed TiO2/GaN nanowire FET with a Si back gate offers a viable strategy for improving gas sensor selectivity at room temperature.
• The tunable back-gate parameter provides a method to differentiate between cross-sensitive gases like NO2 and SO2.
• While device geometries require optimization, the proof-of-concept validates the potential of this approach for selective gas sensing applications.