Characterization of liquid-phase sensor utilizing GaN-based two-terminal device

In this paper, the sensitivity of GaN surfaces in aqueous solutions and polar liquids has been investigated. For this purpose, two terminal devices fabricated on bulk Si doped-GaN structures and undoped-AlGaN/GaN heterostructures with unpassivated open area are used to measure the responses to the changes of the H⁺ concentration in aqueous solutions and the dipole moment in polar liquids. Two material structures are used in this study. They are Si-doped GaN bulk structures and undoped AlGaN/GaN HEMT. The same structures, conditions and fabrication processes have been applied for both material samples. The fabricated devices are shown. The mesa channel is patterned using photolithography and reactive ion etching where SiO₂ layer is applied as a mask.