Abstract
A Pd-functionalized hydrogen gas sensor was fabricated on an AlGaN/GaN-on-Si heterostructure platform. The AlGaN layer under the Pd catalyst area was partially recessed by plasma etching, which resulted in a low standby current level enhancing the sensor response. Sensor stability and power consumption depending on operation conditions were carefully investigated using two different bias modes: constant voltage bias mode and constant current bias mode. From the stability point of view, high voltage operation is better than low voltage operation for the constant voltage mode of operation, whereas low current operation is preferred over high current operation for the constant current mode of operation. That is, stable operation with lower standby power consumption can be achieved with the constant current bias operation. The fabricated AlGaN/GaN-on-Si hydrogen sensor exhibited excellent sensing characteristics; a response of 120% with a response time of < 0.4 s at a bias current density of 1 mA/mm at 200 °C. The standby power consumption was only 0.54 W/cm2 for a sensing catalyst area of 100 × 24 μm2.
Highlights
Hydrogen has attracted much attention as a new energy source, and extensive research has been conducted [1] into its use
Field-effect transistor (FET)-type hydrogen gas sensors were fabricated on an AlGaN/GaN-on-Si
A Pd-functionalized hydrogen sensor fabricated on an AlGaN/GaN-on-Si heterostructure platform was investigated under different operation conditions
Summary
Hydrogen has attracted much attention as a new energy source, and extensive research has been conducted [1] into its use. Hydrogen is used as the material for fuel cells and has been highlighted as a pollution-free natural energy source [2]. Reliable hydrogen gas sensors with fast response characteristics are required to identify and prevent hydrogen leakage in fuel cells. Various semiconductor materials have been utilized to implement hydrogen sensors [4,5,6,7,8,9,10], among which GaN is an attractive material for a hydrogen sensor operating at high temperatures because of its wide energy bandgap with low intrinsic carrier density [11,12,13]. The low intrinsic carrier density allows GaN to maintain its semiconductor properties in high-temperature environments. AlGaN/GaN heterostructure materials have the added benefit of high electron concentrations of a two-dimensional electron gas channel with a high channel mobility of >1500 cm2 /V·s, which enhance the response speeds
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