Mechanism of Hydrogen Sensing by AlGaN/GaN Pt-Gate Field Effect Transistors: Magnetoresistance Studies

Physical mechanism responsible for hydrogen sensing by AlGaN/GaN transistors was investigated. Original resistance studies versus magnetic fields (up to 8T) were used to determine precisely hydrogen induced change of carrier mobility and density. Results clearly show that the carrier mobility change is responsible for less than five percent and that the hydrogen sensitivity is mainly related (more than 95 percent) to the carrier density change. These results support the physical model that relates hydrogen sensing with a change of surface charges resulting in modification of the GaN depletion layer