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 (I_DS) is improved ∼ 32% after the H₂O₂ oxidation due to the passivation effect. In addition, extrinsic transconductance (g_m) 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 (ψ_s) 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.