Charging mechanism of AlGaN/GaN open-gate pH sensor and electrolyte interface

The charging mechanism of the interface between an AlGaN/GaN based open-gate ion-sensitive field-effect transistor and electrolyte is studied theoretically. Density functional theory calculations are performed to obtain the energy minimum structure of the surface oxide and electrolyte interface. Thermodynamics based relations are employed to obtain the double layer parameters. An analytical model is applied to study the carrier density modulation of the AlGaN/GaN heterostrucrure by the influence of the surface charge.