Chemical sensing with GaN based devices

In this contribution we summarize recent results on the detection principles of chemical sensors based on GaN field effect devices. An intermediate native oxide layer is shown to be the origin for the hydrogen sensitivity of Pt/Pd:GaN Schottky diodes, as it supplies adsorption sites for atomic hydrogen, dissociated at the catalytic Schottky contact. AlGaN/GaN heterostructure field effect transistors are demonstrated to exhibit a high pH sensitivity when operated in electrolyte solutions. A comparison of different surface treatments reveals that also in this case a native metal oxide layer causes an almost Nernstian linear sensitivity and allows stable operation with low drift.