pH sensors are monitoring devices with wide applications in biology, chemistry, medicine, and agriculture. To enhance their sensitivity and long-term stability, efficient study of such devices becomes imperative but is impossible without the aid of accurate analytical models. A new analytical model for the pH sensing characteristics of AlGaN/GaN-based high-electron-mobility transistors (HEMTs) is presented herein, as well as theoretical predictions and optimization of the charge sensitivity for ungated AlGaN/GaN HEMT-based pH sensors. The change in the drain current with the changing surface potential due to a variation in the pH of the electrolyte is calculated for devices with different Al mole fractions, AlGaN thicknesses, gate length spacings, and passivation layers. The numerical values for the drain current, threshold voltage, and surface potential obtained by using this new model show good agreement with available experimental results. It is demonstrated that the sensitivity of GaN HEMT-based pH sensors at lower pH values can be improved by applying a SiN_x passivation layer to the HEMT. The calculated average root-mean-square error of our model is 0.018, being an order of magnitude lower than other models reported in literature.

pH传感器是监视设备，在生物学，化学，医学和农业中具有广泛的应用。为了提高其灵敏度和长期稳定性，必须对此类设备进行有效的研究，但是，如果没有准确的分析模型的帮助，这是不可能的。本文介绍了一种基于AlGaN / GaN的高电子迁移率晶体管（HEMT）的pH感测特性的新分析模型，以及针对非电化的基于AlGaN / GaN HEMT的pH传感器的理论预测和电荷敏感性的优化。对于具有不同Al摩尔分数，AlGaN厚度，栅极长度间距和钝化层的器件，计算了由于电解质pH值变化而导致的漏极电流随表面电位变化而发生的变化。漏极电流，阈值电压，使用该新模型获得的表面电势与可用的实验结果显示出良好的一致性。结果表明，通过应用SiN可以提高基于GaN HEMT的pH传感器在较低pH值下的灵敏度_x HEMT的钝化层。我们模型的平均均方根误差为0.018，比文献中报道的其他模型低一个数量级。