Insulated-gate field-effect transistors

H. Shichman andD. Hodges. Modelling and simulation of insulated-gate field effect transistor switching circuits , IEEE Journal of Solid-State Circuits SC3 (1968), 285-289. 

M. S. Mock, A time dependent numerical model of the insulated gate field effect transistor, Solid State Electronics, 24 (1981), pp. 959-966. 

Field-Effect Transistors (FETs) are part of all modern pH meters. With the introduction of ion-sensitive field-effect transistors, they have both been brought to the attention of chemists. In order to understand the principles of operation of these new electrochemical devices, it is necessary to include the FET in the overall discussion of the electrochemical cell. The outline of the operation of an insulated gate field-effect transistor is given in Appendix C. 

Fig. 6.31 Insulated gate field-effect transistor (IGFET) with electronically conducting, chemically selective gate...

Field-effect transistors (Appendix C) are miniature cousins of the Kelvin probe. The most common is the insulated gate field-effect transistor. The heart of the insulated gate field-effect transistor is the Metal-Insulator-Semiconductor (MIS) capacitor. Let us form this capacitor from palladium (to be modulated by hydrogen), silicon dioxide (insulator), and p-type silicon (semiconductor), and examine the energy levels in this structure (Fig. 6.32). 

According to the IEEE standard test methods for the characterisation of OFETs [26], the Shockley equations for insulated gate field effect transistors (IGFETs) are used to approximate the field-indueed drain eurrent in the organic material between the drain and source contaets. It should be reeom-mended that the following assumptions form the basis of the applieability of the equations ... 

The basic idea that guides the insulated-gate field-effect transistor (FET) traces back to the mid-1920s [14], but it was not until 1960 that this early concept could be successfully demonstrated, with the invention of the metal-oxide-semiconductor FET (MOSFET) [15]. Field-effect measurements on copper phthalocyanine films were... 

IGFET insulated-gate field effect transistor... 

The key issue in these sensors is the interface between the ion selective membrane and the contact. The most convenient way to present this problem is in the form of the equivalent electrical circuit in which the resistances and capacitances have their usual electrochemical meaning (Fig.2). It is necessary to include the electrometer (or at least its input stage) in the analysis of these sensors. In most modern instruments the amplifier is an insulated gate field-effect transistor (IGFET) which has the input dc resistance of greater than 10 and the input capacitance on the order of picofarads. 

The essential principle of an active matrix display is that each pixel has associated with it a semiconductor device that is used to control the operation of that pixel. It is this rectangular array of semiconductor devices (the active matrix) that is addressed by the drive circuitry. The devices, which are fabricated by thin-film techniques on the inner surface of a substrate (usually glass) forming one wall of the LCD cell, may be either two-terminal devices (Fig. 6) or three terminal devices (Fig. 7). Various two-terminal devices have been proposed ZnO varistors, MIM devices, and several structures involving one or more a-Si diodes. Much of the research effort, however, has concentrated on the three-terminal devices, namely thin-film, insulated-gate, field-effect transistors. The subject of thin-film transistors (TFTs) is considered elsewhere in this volume suffice it to say that of the various materials that have been suggested for the semiconductor, only a-Si and poly-Si appear to have serious prospects of commercial exploitation. 

Several types of field-effect transistors (FETs) have been developed and are widely used in integrated circuits. One of these, the insulated-gate field-effect transistor, was the outgrow th of the need to increase the input resistance of amplifiers. Typical insulated-gale... 

CHEMFET devices or chemically sensitive field-effect transistors are potentiometric devices in which the metal layer of a solid-state insulated gate field-effect transistor (IGFET) f29] is replaced with a chemically sensitive electroconductive polymer membrane film. Changes in polymer membrane potential modulate the drain impedance of the space-charge region beneath the insulator. The result is a change in drain current /o under a fixed drain voltage Vd- The potential of the membrane may be modulated in the standard way (as in po-tentiometry, above) or may be modulated by an inert electrode placed beneath the film (but isolated from both the source and drain electrodes) and connected to an efficient electrode for the candidate analyte [30]. 

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