180 CHEMICAL SENSORS. VOLUME 5: ELECTROCHEMICAL AND OPTICAL SENSORS Table 4.1. Major breakthroughs in ISFET technology Y EAR 1970 1983 2002 R ESEARCHERS P. Bergveld J. Van der Spiegel, I. Lauks, P. Chan, and D. Babic M. J. Schöning, A. Simonis, C. Ruge, H. Ecken, M. Müller-Veggian, and H. Lüth Y. Liu and T. Cui D EVICE STRUCTURE Ion-sensitive field-effect transistor (ISFET) Extended-gate field-effect transistor (EGFET) Electrolyte-insulator-semiconductor (EIS) field-effect sensor using macroporous silicon ISFET fabrication by nano self-assembly technique 2007 excitation is strongly suppressed (Schmid 2006). GaN-based ISFETs have high sensitivity, approaching Nernstian response. Biocompatibility of this material makes it very useful for biomedical applications. Table 4.1 presents at a glance the milestones in ISFET development. A comparison of ISFET, EGFET, and EIS field-effect sensors is given in Table 4.2. Table 4.2. ISFET, EGFET, and EIS structures