The effect of substrate-gate bias on the zinc oxide field-effect transistor for biosensing application

This paper studies the application of substrate-gate (SG) bias on the electrical characteristics of a zinc oxide (ZnO) field-effect transistor (FET) structure for biosensing application. A commercial numerical simulation, Silvaco ATLAS is utilized in simulation process and the impacts of various substrate-gate voltage (V
SG
) on the device structure, in terms of electron concentration and current-voltage (I–V) characteristics of the FET-based biosensor are investigated. Application of negatively V
SG
has shifted the threshold voltage (V
T
) of the device toward lower drain voltage (V
D
) and increased the drain current (I
D
) across source (S) and drain (D), while application of positive V
SG
has given a contradict effects. In addition, the surface of ZnO thin film are introduced with interface charge (Q
F
), representing charged target molecule for biosensing application. These effects on the device have given a helpful indication for a practical fabrication process and for biosensor applications.