Investigation of Hydrogen-Sensing Characteristics of a Pd/GaN Schottky Diode

The hydrogen sensing and response characteristics of a catalytic Pd/GaN metal-semiconductor (MS) Schottky diode are systematically studied in this paper. The current-voltage characteristics, hydrogen detection sensitivity ratios, Schottky barrier height variations, adsorption heat, and transient responses for different hydrogen concentration are measured over wide temperature range. The Pd/GaN Schottky diode reveals a remarkable capability of hydrogen detection at high temperature and relatively wide operating temperature range under bipolarly applied voltages. Experimentally, extremely low hydrogen concentration for 14 ppm H(2) in air can be detected. A very high hydrogen detection sensitivity ratio of 12744 and a large Schottky barrier height variation Delta phi(b) of 253 meV are obtained when a 9970 ppm in air gas is introduced at 300 K. In addition, according to the van't Hoff equation, the hydrogen adsorption heat value of the studied device is calculated as -18.24 kJ mole(-1). Finally, considerably short response time is found in the studied device.