Resolution of hydrogen and carbon monoxide on metal gate GaN MODFET sensors

A low-cost sensor array capable of detecting 10 ppm CO in hydrogen (30%-75%) is described. Results are presented indicating the cross-sensitivity of CO (0-80 ppm) and hydrogen (30%-70%) on gallium nitride (GaN) modulation-doped-field-effect-transistor (MODFET) sensors with catalytic metal gates. A method was developed for resolving the CO and hydrogen concentrations using an array of GaN MODFET sensors. The method is demonstrated with rhodium. (Rh) and platinum (Pt) gate GaN MODFET sensors and a two-component calibration matrix of 25 pairs of CO and hydrogen. concentrations. The measurements of gate voltage at each of the 25 calibration points are used to compute a three-dimensional response surface. The intersection of the response surfaces for the Pt and Rh sensors is used to resolve and measure the concentrations of CO and hydrogen. The data suggest the detection of CO at 10 ppm is possible over most of the range.