Highly sensitive ion sensor based on the MOSFET-BJT hybrid mode of a gated lateral BJT

In this study, a highly sensitive ion sensor using a gated lateral bipolar junction transistor (BJT) was proposed and evaluated. The proposed device was developed using a semiconductor technology that combined the MOSFET and the BJT structures. We found that the sensitivity of the conventional semiconductor-based sensors has a large dependence on the transconductance of the device. Therefore, a MOSFET-BJT hybrid-mode-operated gated lateral BJT structure ion sensor was developed that has higher transconductance than MOSFET sensor devices. In order to confirm the characteristics of the sensor device, the V_G-I_E curve, transconductance, and current gain performance were evaluated and compared between the MOSFET mode and MOSFET-BJT hybrid mode. Then, ion detection experiments were performed using pH buffer solutions. The evaluation results indicated that the sensitivity of the MOSFET-BJT hybrid mode can be controlled by altering the base current and is higher (21.77 μA/pH) than the sensitivity of the MOSFET mode, which is similar to the conventional MOSFET-structure-based ISFET (17.56 μA/pH). Further, this study proved that in the MOSFET-BJT hybrid mode, the proposed device has higher transconductance and current gain characteristics.