title: Novel H⁺-Ion Sensor Based on a Gated Lateral BJT Pair.
abstract: An H⁺-ion sensor based on a gated lateral bipolar junction transistor (BJT) pair that can operate without the classical reference electrode is proposed. The device is a special type of ion-sensitive field-effect transistor (ISFET). Classical ISFETs have the advantage of miniaturization, but  they are difficult to fabricate by a single fabrication process because of the bulky and brittle reference electrode materials. Moreover, the reference electrodes need to be separated from the sensor device in some cases. The proposed device is composed of two gated lateral BJT components, one of which had a silicide layer while the other was without the layer. The two components were operated under the metal-oxide semiconductor field-effect transistor (MOSFET)-BJT hybrid mode, which can be controlled by emitter voltage and base current. Buffer solutions with different pH values were used as the sensing targets to verify the characteristics of the proposed device. Owing to their different sensitivities, both components could simultaneously detect the H⁺-ion concentration and function as a reference to each other. Per the experimental results, the sensitivity of the proposed device was found to be approximately 0.175 μA/pH. This experiment demonstrates enormous potential to lower the cost of the ISFET-based sensor technology.
authors.affiliation: Science and Technology on Inertial Laboratory, Beihang University, No. 37 Xueyuan Road, Beijing 100191, China. hengyuan@buaa.edu.cn.
authors.forename: Heng
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Science and Technology on Inertial Laboratory, Beihang University, No. 37 Xueyuan Road, Beijing 100191, China. zhangjixing@buaa.edu.cn.
authors.forename: Jixing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Science and Technology on Inertial Laboratory, Beihang University, No. 37 Xueyuan Road, Beijing 100191, China. caochuangui@buaa.edu.cn.
authors.forename: Chuangui
authors.initials: C
authors.lastname: Cao
authors.affiliation: Science and Technology on Inertial Laboratory, Beihang University, No. 37 Xueyuan Road, Beijing 100191, China. zhanggangyuan@buaa.edu.cn.
authors.forename: Gangyuan
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, No. 422 South Siming Road, Xiamen 361005, China. shaodazhang@hotmail.com.
authors.forename: Shaoda
authors.initials: S
authors.lastname: Zhang
keywords: ISFET; MOSFET–BJT hybrid; gated lateral BJT; ion sensor