Room temperature carbon monoxide sensor using ITO/n-GaAs Schottky contact

In this paper we report the potential of ITO/n-GaAs Schottky diode sensor for carbon monoxide detection at room temperature. The ITO/n-GaAs Schottky contacts were developed using an evaporation system in our laboratory. Due to the very low operating temperature of the diode which shows rapid response to carbon monoxide (CO) it can be applied to micro-sized devices for IC technology. It has been found that the diode exhibited a saturation current of 1×10−10 A at room temperature in the absence of CO gas, whereas a value of 1.1×10−9 A was obtained for saturation current at room temperature in the presence of 1000 ppm CO gas. This excellent responsivity of ITO/n-GaAs diode sensor at room temperature can be due to penetration of CO molecules into the thin ITO layer (150 nm) and changing its work function to a lower value to form a lower Schottky barrier. A comparative study showed that Schottky gas sensor fabricated with gold metal contact presented different sensitivities to CO gas. The relation between different Schottky contacts subjected to carbon monoxide is discussed.