Performance Analysis of Open-Gate Junction FET: A New Foundry-Based Silicon Transistor for Biochemical Sensing Applications

This paper investigates the performance and parametric design of a new foundry-based silicon field-effect transistor (FET) sensing platform known as the open-gate junction field-effect transistor (OG-JFET) for bio/chemical sensing applications. The fabrication process of the OG-JFET relies on a standard foundry process, requiring the establishment of parametric design rules to understand the effect of crucial sensor performance factors, including transconductance (g $_{\mathrm {m}}$ ) and device efficiency ( $\eta =$ gm/I $_{\mathrm {ds}}$ ). The study examines the impact of various geometric parameters (e.g., channel length and thickness) and material-related parameters (such as boron and phosphorous impurity doping levels) on sensor performance. Simulations provide insights and guidelines for the efficient design and characterization of the OG-JFET, focusing on enhancing gm and maximizing $\eta $ for biosensing applications. Experimental measurements of the OG-JFET demonstrate a current range of $\sim ~200~\mu $ A/ $\mu $ m, a high gm of approximately $\sim ~1700~\mu $ S ( $340~\mu $ S/ $\mu $ m), and $\eta $ of $\sim ~4.5$ V−1 (for a channel length of $5~\mu $ m), which are of importance for circuit design and biosensing application of OG-JFET. These results showcase the performance of this sensor compared to other silicon-based FET platforms for internal signal amplification in sensing applications of OG-JFET. The findings of this paper offer valuable guidelines for the design of sensors based on OG-JFET technology, enabling gaining insights into the impact of sensor structure on sensing performance. Also, we have demonstrated how two performance parameters can be utilized to compare two different designs of OG-JFET, which is useful for future designers.