Oxide semiconductor-gate field effect

The attractiveness of silicon as a semiconductor material for ICs derives in part from the feet that this important material forms a naturally insulating surface oxide. Use is made of this fact, for example, in metal-oxide-semiconductor (MOS) field-effect transistors (FET), where the oxide serves as the gate insulator. No such naturally insulating oxide occurs with any of the compound semiconductors that offer improved performance over silicon in many device apphcations. Roberts et al. (38) demonstrated the feasibiUty of such metal-insulator-semiconductor (MIS) structures as FETs and chemical sensors shown schematically in Figure 1.23. These researchers... 

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... 

This approach has been developed using commercial resistive-type metal oxide semiconductor sensors - for example, for early fire detection in coal mines (Lee and Reedy, 1999 Reimann et al, 2009). This concept is now also under development for field effect sensor devices based on SiC for the detection and quantification of, for example, NO2. It has initially been demonstrated that discrimination between different gases (such as H2, NH3 and CO) and different concentrations seems possible for both Pt and Ir gate field effect sensors (Bur et al, 2010 Bur et a/., 2011a). 

Figure Bl.22.4. Differential IR absorption spectra from a metal-oxide silicon field-effect transistor (MOSFET) as a fiinction of gate voltage (or inversion layer density, n, which is the parameter reported in the figure). Clear peaks are seen in these spectra for the 0-1, 0-2 and 0-3 inter-electric-field subband transitions that develop for charge carriers when confined to a narrow (<100 A) region near the oxide-semiconductor interface. The inset shows a schematic representation of the attenuated total reflection (ATR) arrangement used in these experiments. These data provide an example of the use of ATR IR spectroscopy for the probing of electronic states in semiconductor surfaces [44]-...

Gate oxide dielectrics are a cmcial element in the down-scaling of n- and -channel metal-oxide semiconductor field-effect transistors (MOSEETs) in CMOS technology. Ultrathin dielectric films are required, and the 12.0-nm thick layers are expected to shrink to 6.0 nm by the year 2000 (2). Gate dielectrics have been made by growing thermal oxides, whereas development has turned to the use of oxide/nitride/oxide (ONO) sandwich stmctures, or to oxynitrides, SiO N. Oxynitrides are formed by growing thermal oxides in the presence of a nitrogen source such as ammonia or nitrous oxide, N2O. Oxidation and nitridation are also performed in rapid thermal processors (RTP), which reduce the temperature exposure of a substrate. 

The ISFET is an electrochemical sensor based on a modification of the metal oxide semiconductor field effect transistor (MOSFET). The metal gate of the MOSFET is replaced by a reference electrode and the gate insulator is exposed to the analyte solution or is coated with an ion-selective membrane as illustrated in Fig. 

The operation principle of these TFTs is identical to that of the metal-oxide-semiconductor field-effect transistor (MOSFET) [617,618]. When a positive voltage Vg Is applied to the gate, electrons are accumulated in the a-Si H. At small voltages these electrons will be localized in the deep states of the a-Si H. The conduction and valence bands at the SiN.v-a-Si H interface bend down, and the Fermi level shifts upward. Above a certain threshold voltage Vth a constant proportion of the electrons will be mobile, and the conductivity is increased linearly with Vg - Vih. As a result the transistor switches on. and a current flows from source to drain. The source-drain current /so can be expressed as [619]... 

D. Landheer, G. Aers, W.R. Mckinnon, M.J. Deen, and J.C. Ranuarez, Model for the field effect from layers of biological macromolecules on the gates of metal-oxide-semiconductor transistors. J. Appl. Phys. 98, 044701-1-15 (2005). 

Field effect transistors are miniature, solid-state, potentiometric transducers (Figure 4.22) which can be readily mass produced. This makes them ideal for use as components in inexpensive, disposable biosensors and various types are being developed. The function of these semiconductor devices is based on the fact that when an ion is absorbed at the surface of the gate insulator (oxide) a corresponding charge will add at the semiconductor... 

Tulevski GS, Miao Q, Fukuto M, Abram R, Ocko B, Ffindak R, Steigerwald ML, Kagan CR, Nuckolls C (2004) Attaching organic semiconductors to gate oxides in situ assembly of monolayer field effects transistors. J Am Chem Soc 126 15048-15050... 

The hydrogen sensitivity of palladinm-oxide-semiconductor (Pd-MOS) strnctnres was first reported hy Lnndstrom et al. in 1975 [61]. A variety of devices can he nsed as field-effect chemical sensor devices (Fignre 2.6) and these are introdnced in this section. The simplest electronic devices are capacitors and Schottky diodes. SiC chemical gas sensors based on these devices have been under development for several years. Capacitor devices with a platinum catalytic layer were presented in 1992 [62], and Schottky diodes with palladium gates the same year [63]. In 1999 gas sensors based on FET devices were presented [64, 65]. There are also a few publications where p-n junctions have been tested as gas sensor devices [66, 67]. 

Metal oxide semiconductor field-effect transistors (MOSFETs) are field effect transistors with a thin film of silicon dioxide between the gate electrode and the semiconductor. The charge on the silicon dioxide controls the size of the depletion zone in the polype semiconductor. MOSFETs are easier to mass produce and are used in integrated circuits and microprocessors for computers and in amplifiers for cassette players. Traditionally, transistors have been silicon based but a recent development is field-effect transistors based on organic materials. 

Ion-Selective Field Effect Transistors [22b,c,d] An ion-selective field effect transistor (ISFET) is a hybrid of an ion-selective electrode and a metal-oxide semiconductor field effect transistor (MOSFET), the metal gate of the MOSFET being replaced by or contacted with a thin film of a solid or liquid ion-sensitive material. The ISFET and a reference electrode are immersed in the solution containing ion i, to which the ISFET is sensitive, and electrically connected as in Fig. 5.37. A potential which varies with the activity of ion i, o(i), as in Eq. (5.38), is developed at the ion-sensitive film ... 

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