Platinum-aluminum nitride-silicon carbide diodes as combustible gas sensors

In this article we report on the novel use of a Pt/AlN/SiC structure as a combustible gas sensor. This device structure was fabricated by depositing a 2000 Angstrom thick layer of AlN on the SiC substrate at 900 degrees C by laser ablation. Catalytic Pt gates were deposited onto the AlN at room temperature either by laser ablation or by rf sputtering. The electrical characteristic of the resultant devices from room temperature to 650 degrees C revealed current rectifying behavior. Most importantly, their electrical characteristic changed in response to propane, propylene, and CO introduced into their ambient at temperatures as low as 250 degrees C. They responded to changing gas composition over a wide range of combustible and oxygen concentrations from lean to fuel rich conditions. The response was a function of the ratio of combustible/oxygen concentration rather than to the absolute combustible concentration. However, this relationship exhibited some degree of combustible specificity. (C) 2000 American Institute of Physics. [S0021-8979(00)06205-8].