Characteristics of CO sensors made by polar and nonpolar ZnO nanowires gated AlGaN/GaN high electron mobility transistor

AlGaN/GaN high electron mobility transistors (HEMTs) with polar and nonpolar ZnO nanowires modified gate exhibit significant changes in channel conductance upon expose to different concentration of carbon monoxide (CO) at room temperature. The ZnO nanowires, grown by chemical vapor deposition (CVD), with perfect crystal quality will attach CO molecule and release electrons, which will lead to a change of surface charge in the gate region of the HEMTs, inducing a higher positive charge on the AlGaN surface, and increasing the piezoinduced charge density in the HEMTs channel. These electrons create an image positive charge on the gate region for the required neutrality, thus increasing the drain current of the HEMTs. The HEMTs source-drain current was highly dependent on the CO concentration. The limit of detection achieved was 400 ppm and 3200ppm in the open cavity with continuous gas flow using a 50x50m2gate sensing area for polar and nonpolar ZnO nanowire gated HEMTs sensor.