A Study of Hydrogen Sensing Performance of Pt–GaN Schottky Diodes

Abstract

The performance of hydrogen-gas detectors based on Pt-GaN Schottky diodes with 24-nm-thick Pt contact was investigated. Current-voltage (I-V) Characteristics were measured in two ambients (e.g., synthetic air (20% O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and 1-vol.% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in synthetic air) at different temperatures. The forward current of the diodes is found to increase significantly upon introduction of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 </sub> into the synthetic air ambient. Analysis of the I-V characteristics as a function of temperature demonstrated that the observed current increase is due to a decrease in the effective barrier height (BH) through a decrease in the Pt work function upon absorption of hydrogen. The decrease in the BH was measured as high as 30 and 152 meV at 25 degC and at 280 degC, respectively, upon introduction of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> into the ambient. The changes in the BH were completely reversible upon restoration of the synthetic air ambient. The sensitivity to the hydrogen gas was investigated in dependence on the operating temperature for 1-vol.% hydrogen in synthetic air. The changes in the forward bias at a constant current density of 3.2 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was 90 and 330 mV at 25 degC and at 310 degC, respectively, upon introduction of 1-vol.% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> into the ambient. Additionally, a significant increase in the sensitivity and a decrease in the response and recovery times have been observed after increasing the operating temperature up to ~310degC