Effects of Substrate Materials on the Electrical Behavior of Pd/AlN/Semiconductor Based Hydrogen Sensors

Abstract

AbstractC-plane textured wurtzite AlN films deposited on both, 3C and 6H SiC as well as Si, have been employed in Pd/AlN/Semiconductor diode Hydrogen sensor structures. The SiC based devices behave as rectifiers and do not show the bias dependent capacitance expected for an MIS structure when reverse biased. The Si based devices, albeit exhibiting rectifying characteristics do show the expected dependence of capacitance on reverse bias, with typical depletion and inversion regions. The SiC based devices show the sensor response as change in bias voltage at constant forward current but the Si based device showed no response in this mode of operation albeit it did respond well in terms of the Hydrogen induces shift of the depletion capacitance vs. bias characteristic. As the AlN itself has the same structure in all cases, the differences in both, electrical characteristics and sensing response mechanism are related to differences in the AlN/Substrate heterojunction resulting from differences in the electronic band structure of the substrates.