Gas sensitivity of silicon carbide-based diode structures

Modification of the electrophysical characteristics of Pt/6H-SiC by hydroge n treatment is investigated. It is found that the change in the bias voltag e of a Pt/6H-SiC structure for a fixed capacitance is related to the hydrog en concentration by the Nernst equation. The sensor response at 150 degrees C is 39 mV per decade of variation of the hydrogen concentration. The chan ges in the forward and reverse currents and the differential resistances of the diode structure in a hydrogen-containing atmosphere are calculated. Th e shift of the current-voltage characteristic toward negative voltages and the decrease in the differential resistance of the junction are caused by a decrease in the height of the potential barrier of the Schottky barrier as a result of dissociative adsorption of hydrogen with the formation of a do uble charged layer at the metal-semiconductor boundary. At a working temper ature around 150 degrees C the characteristics of the structures are stable . We also investigated the effect of a temperature anneal (500 degrees C). The formation of platinum silicides at this temperature leads to degradatio n of the gas-sensitive properties of the metal-semiconductor junction. (C) 1999 American Institute of Physics. [S1063-7842(99)01002-8].