Search

Pt contacted AlGaN/GaN high electron mobility transistors with Sc2O3 gate dielectrics show reversible changes in drain–source current upon exposure to H2-containing ambients, even at room temperature. The changes in current (as high as 3 mA for relatively low gate voltage and drain–source voltage) are approximately an order of magnitude larger than for Pt/GaN Schottky diodes and a factor of 5 larger than Sc2O3/AlGaN/GaN metal–oxide–semiconductor (MOS) diodes exposed under the same conditions. This shows the advantage of using a transistor structure in which the gain produces larger current changes upon exposure to hydrogen-containing ambients. The increase in current is the result of a decrease in effective barrier height of the MOS gate of 30–50 mV at 25 °C for 10% H2/90% N2 ambients relative to pure N2 and is due to catalytic dissociation of the H2 on the Pt contact, followed by diffusion to the Sc2O3/AlGaN interface. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An AlGaN/GaN high electron mobility transistor structure was used for sensing different liquids present in the gate region. The forward current showed significant decreases upon exposure of the gate area to solvents (water, acetone) or acids (HCl). The pH sensitivity is due to changes in net surface charge that affects the relative depletion in the channel of the transistor. The results indicate that nitride-based heterostructures may have application in integrated chemical, gas and fluid monitoring sensors. [Copyright &y& Elsevier]