Hydrogen gas sensors employ an epitaxial layer of the thermodynamically
stable form of aluminum nitride (AlN) as the "insulator" in an MIS structure having
a thin metal gate electrode suitable for catalytic dissociate of hydrogen, such
as palladium, on a semiconductor substrate. The AlN is deposited by a low temperature
technique known as Plasma Source Molecular Beam Epitaxy (PSMBE). When silicon (Si)
is used the semiconducting substrate, the electrical behavior of the device is
that of a normal nonlinear MIS capacitor. When a silicon carbide (SiC) is used,
the electrical behavior of the device is that of a rectifying diode. Preferred
structures are Pd/AlN/Si and Pd/AlN/SiC wherein the SiC is preferably 6H-SiC.