Improved Sensing Characteristics of a Novel $\hbox {Pt} \hbox {/HfTiO}_{2}\hbox {/SiC}$ Schottky-Diode Hydrogen Sensor

A novel metal-insulator-silicon carbide Schottky-diode hydrogen sensor with HfTiO₂ gate insulator annealed in three different gases (N₂, O₂, or NO) is fabricated. Measurements are carried out at various hydrogen concentrations at high temperature using a computer-controlled measurement system. The hydrogen-sensing characteristics of the devices are studied with the help of ellipsometry, transmission electron microscopy, scanning electron microscope, energy-dispersive spectroscopy, and atomic force microscopy. Experimental results show that these sensors have high sensor output and can give significant response even at low hydrogen concentration. This work also finds that the NO-annealed sensor has the highest sensor output. When 800-ppm H₂ in N₂ gas is introduced, the NO-annealed sensor exhibits a high sensor output of 782% at 450°C, which is about three and six times higher than those of the O₂- and N₂-annealed sensors, respectively. As compared to another sensor with HfO₂ gate insulator annealed in NO, the proposed NO-annealed sensor shows higher sensor output, which should be mainly attributed to the larger barrier height at the metal-insulator interface. The excellent hydrogen-sensing characteristics of this novel sensor make it very suitable for detecting hydrogen leakage, particularly in high-temperature environments.