A study of Pd/Si MIS Schottky barrier diode hydrogen detector

Pd/Si MIS Schottky diode hydrogen detectors have been fabricated with a response of 2-3 orders of magnitude change in current for 154 ppm of H2in N2. Detailed evaluation of dark I-V, C-V, illuminated I-V, and internal photoemission data unambiguously ascribes the strong hydrogen sensitivity of these diodes to hydrogen-induced change in the work function of Pd, rather than to any surface-state effects. The reaction rate of the device to different gas ambients has been studied with time response measurements. A long-term degradation mechanism has been identified and traced to the poisoning of Pd by environmental sulfur. The role of oxygen and atomic hydrogen in determining the Schottky barrier height also is discussed in some detail.