Enhanced Performances of AlGaN/GaN Ion-Sensitive Field-Effect Transistors Using H2O2-Grown Al2O3 for Sensing Membrane and Surface Passivation Applications

This paper uses H₂O₂ oxidation technique to grow Al₂O₃ on AlGaN/GaN heterostructure. The H₂O₂-grown-Al₂O₃ is served as a sensing membrane and a surface passivation layer. The contact angle of the ion-sensitive field-effect transistor (ISFET) with the H₂O₂-grown-Al₂O₃ is improved from 66.5° to 40.6° and this phenomenon indicates that the hydrophile characteristic is improved after the H₂O₂ treatment. The drain-source current (IDS) is improved ~32% after the H₂O₂ oxidation due to the passivation effect. In addition, extrinsic transconductance (gm) characteristics of the transistors are investigated. The pH sensitivity is also improved from 41.6 to 55.2 mV/pH for the ISFET with H₂O₂-grown-Al₂O₃. Furthermore, the ISFET with the H₂O₂ treatment exhibits better transient characteristics compared with the ISFET without the H₂O₂ treatment. The sensitivity parameter (β) and the relationship between surface potential (ψs) and pH value are investigated by theoretical calculation. The hysteresis phenomenon and the drift effect can be improved using the present H₂O₂-grown Al₂O₃ as the sensing membrane and the passivation layer.