AlGaN/gallium nitride (GaN) ion-sensitive field-effect transistors (ISFETs) were fabricated as pH sensors. The sensitivity of the AlGaN/GaN ISFETs was evolved with gate recess process and ammonium hydroxide (NH ₄ OH) treatment. By performing the gate recess process, the threshold voltage ( ${V}_{\text {T}}$ ) of the ISFET increased from −3.33 to −0.31 V and the maximum conductance ( ${G}_{\text {M}}$ ) of the ISFET increased from 0.8 to 2 mS, with the current sensitivity of the pH sensor improving from 52.25 to $78.86~\mu \text{A}$ /pH. Further, after performing the ammonium hydroxide treatment, the ${V}_{\text {T}}$ of the ISFET increased from −0.33 to −0.14 V, with the current sensitivity of the pH sensor improving from 78.86 to $84.39~\mu \text{A}$ /pH. To characterize the surface conditions the X-ray photoelectron spectroscopy (XPS) was deployed. The results indicated that many nitrogen vacancies ( ${V}_{\text {N}}$ ) were introduced during the recess process, leading to a negative ${V}_{\text {T}}$ shift and a smaller potential sensitivity ( ${S}_{V}$ ), which can be improved by ammonium hydroxide treatment.

中文翻译：

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通过凹进工艺和氢氧化铵处理提高了AlGaN / GaN离子敏感型场效应晶体管的pH敏感性

制作了AlGaN /氮化镓（GaN）离子敏感型场效应晶体管（ISFET）作为pH传感器。AlGaN / GaN ISFET的灵敏度是通过栅极凹陷工艺和氢氧化铵（NH ₄ OH）处理得到的。通过执行栅极凹进工艺，阈值电压（ $ {V} _ {\ text {T}} $ ISFET的）从-3.33增至-0.31 V，最大电导（ $ {G} _ {\ text {M}} $ ）的ISFET值从0.8增至2 mS，pH传感器的电流灵敏度从52.25改善至 $ 78.86〜\ mu \ text {A} $ / pH。此外，在进行氢氧化铵处理后， $ {V} _ {\ text {T}} $ ISFET的电流从-0.33增至-0.14 V，pH传感器的电流灵敏度从78.86提高至 $ 84.39〜\ mu \ text {A} $ / pH。为了表征表面条件，部署了X射线光电子能谱（XPS）。结果表明，许多氮空位（ $ {V} _ {\ text {N}} $ ）是在休会期间引入的，导致负面影响 $ {V} _ {\ text {T}} $ 偏移和较小的电位灵敏度（ $ {S} _ {V} $ ），可以通过氢氧化铵处理加以改善。