Comparison of hydrogen sensing characteristics for Pd/GaN and Pd/Al0.3Ga0.7As Schottky diodes

The hydrogen sensing characteristics of Pd/GaN and Pd/Al0.3Ga0.7As Schottky diodes are systematically studied and compared over wide hydrogen concentration and temperature ranges. Experimentally, upon exposing to hydrogen-containing gases, both of the studied Schottky-type hydrogen sensors can be operated under bi-polarity applied voltages attributed to the substantial increases of forward- and reverse-biased currents with increasing the hydrogen concentration. The Pd/GaN Schottky diode can be operated under higher temperature with larger Schottky barrier height modulation than that of Pd/Al0.3Ga0.7As. According to the van’t Hoff equation, the hydrogen adsorption heat values are −18.24 and −10.36 kJ mol−1 for the Pd/GaN and Pd/Al0.3Ga0.7As Schottky diodes, respectively. Experimentally, the Pd/Al0.3Ga0.7As and Pd/GaN Schottky diodes manifest faster adsorption and desorption responses at higher temperature (≥400 K).