Ion sensitive Field Effect Transistors (ISFETs) Basics and Applications

Microfabricated semiconductor devices are essential components of many biochemical sensors today, and show great potential for advanced devices in the future. Since the proposal of an pH sensitive device, based on the technology of field effect transistors, was made in the early seventies, these so called ISFETs have been of great interest for the application in chemical and biological sensing devices. In this report, the physical and technical basics of these systems are discussed. Starting with the introduction of MOSFETs and their operation, ion sensitivity of the oxide surface is explained by the application of the site binding model. To give an overview about recent and future applications of ISFETs for sensing and physiological measurements, modified ISFETs (ENFETs, BIOFETs, DNA-sensors) as well as sensor/actuator systems are presented. Modern research is also focusing on the application of new materials. In particular, wide bandgap semiconductors like diamond and GaN show interesting properties, with respect to biochemical sensing devices.