Abstract An a-IGZO based dual gate ion sensitive field effect transistor (DG ISFET) was fabricated utilizing a simple and cost effective method. Sputtered Al2O3 was used as the top gate dielectric to obtain a greater surface site density and thus a higher sensitivity due to higher surface roughness. Deteriorated characteristics of the bottom gate thin film transistor (BG TFT) caused by deposition of Al2O3, attributed to the induced oxygen vacancies at the Al2O3/a-IGZO interface were recovered by optimized annealing at 350 °C in presence of oxygen. The increased value of the OFF current (~nA) in the BG TFT upon exposure to the electrolyte (pH-4), was attributed to the formation of double channels in the active (a-IGZO) layer. The conduction in the channel formed at the Al2O3/a-IGZO interface dominated over the bottom gate channel (a-IGZO/SiO2 interface) in the turn OFF region while being comparable in the turn ON region. The fabricated DG ISFET showed ~6-fold enhancement in pH sensitivity (347.6 mV/pH) from the Nernst's limit (59 mV/pH). To validate the experimental findings, a T-CAD based simulation model was proposed by incorporating three dielectric layers to represent the electric double layer formed at the electrolyte/insulator interface and at the reference electrode.

中文翻译：

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使用 Al2O3 作为顶栅电介质的基于 a-IGZO 的双栅 ISFET pH 传感器的界面机制

摘要 利用简单且成本有效的方法制造了基于 a-IGZO 的双栅极离子敏感场效应晶体管 (DG ISFET)。溅射的 Al2O3 被用作顶栅电介质以获得更大的表面位点密度，从而由于更高的表面粗糙度而获得更高的灵敏度。底栅薄膜晶体管（BG TFT）由于在 Al2O3/a-IGZO 界面处引起的氧空位沉积而导致的性能恶化通过在 350°C 下优化退火并在氧存在下进行恢复。在暴露于电解质 (pH-4) 时，BG TFT 中关断电流 (~nA) 的增加值归因于活性 (a-IGZO) 层中双通道的形成。在 Al2O3/a-IGZO 界面形成的沟道中的传导在关断区域主导底栅沟道（a-IGZO/SiO2 界面），而在导通区域则具有可比性。制造的 DG ISFET 显示出比能斯特极限 (59 mV/pH) 的 pH 灵敏度 (347.6 mV/pH) 提高了约 6 倍。为了验证实验结果，提出了一个基于 T-CAD 的模拟模型，通过结合三个介电层来表示在电解质/绝缘体界面和参考电极处形成的双电层。