Performance Optimization of Nitrogen Dioxide Gas Sensor Based on Pd-AlGaN/GaN HEMTs by Gate Bias Modulation

Area of Science:

• Materials Science
• Semiconductor Devices
• Chemical Sensing

Background:

• High electron mobility transistors (HEMTs) offer potential for gas sensing applications due to their high sensitivity.
• Nitrogen dioxide (NO2) is a harmful pollutant requiring accurate and reliable detection methods.
• Optimizing sensor performance at high temperatures is crucial for industrial and environmental monitoring.

Purpose of the Study:

• To investigate and optimize the sensing characteristics of Pd-AlGaN/GaN HEMTs for NO2 detection at high temperatures.
• To demonstrate the advantages of field-effect transistor (FET)-type sensors over diode-type sensors through gate bias optimization.
• To evaluate the impact of gate bias on electron density modulation and its correlation with gas sensing performance.

Main Methods:

• Fabrication of Pd-AlGaN/GaN HEMT structures.
• Gas sensing measurements of NO2 at high temperatures (300 °C).
• Systematic variation of gate bias (V_G) to study its effect on sensor response and kinetics.

Main Results:

• Gate bias significantly optimizes NO2 sensing performance, highlighting FET-type sensor advantages.
• Biasing near the threshold voltage maximizes electron density changes upon gas exposure, enhancing sensitivity.
• At 300 °C and 100 ppm NO2, sensitivities of 26.7% (V_G = 0 V) and 91.6% (V_G = -1 V) were achieved.
• Response times improved from 32 s to 9 s with gate bias adjustment (V_G = 0 V to V_G = -1 V).

Conclusions:

• Gate bias is a critical parameter for optimizing NO2 detection using Pd-AlGaN/GaN HEMT sensors at high temperatures.
• FET-type HEMT sensors exhibit superior sensitivity and faster response times compared to diode-type sensors when gate bias is optimized.
• The developed sensor demonstrates stable repeatability at high temperatures, making it suitable for reliable gas monitoring applications.