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 H₂ in air can be detected. A very high hydrogen detection sensitivity ratio of 12744 and a large Schottky barrier height variation Δφ_b of 253 meV are obtained when a 9970 ppm H₂ 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. Finally, considerably short response time is found in the studied device.