Field-effect transistor dielectrics

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. 

Facchetti A, Yoon MH, Marks TJ (2005) Gate dielectrics for organic field-effect transistors new opportunities for organic electronics. Adv Mater 17(14) 1705-1725... 

Fig. 20 Charge carrier mobility in P3HT as a function of the charge carrier concentration. Squares refer to an experiment performed on a field effect transistor while circles refer to experiments done on an electrochemically doped sample. In the latter case the mobility is inferred from the steady state current at a given doping level. Solid and dashed lines have been fitted using the theory of [101]. The fit parameters are the site separation a, the prefactor Vq in the Miller-Abrahams-type hopping rate, the inverse wavefunction decay parameter y and the dielectric constant e. From [101] with permission. Copyright (2005) by the American Institute of Physics...

Kim S, Nah J, Jo I et al (2009) Realization of a high mobility dual-gated graphene field-effect transistor with AI2O3 dielectric. Appl Phys Lett 94 062107... 

The contact problems are mitigated in the hybrid ion sensor by making the internal conductor shorter and shorter until it is more natural to talk about its thickness rather than its length. The material of this internal contact has not changed during this transition and neither has the electrochemistry at the interface. Thus, the only difference between the coated wire and the hybrid sensor is the length (or thickness) of the contact. We therefore skip it and go directly to the solid-state ISFET, in which the thickness of the internal contact is zero. In other words, the ion-selective membrane is placed directly at the input dielectric of the field-effect transistor (Fig. 6.20). 

Pentacene routinely yields field-effect transistor (FET) devices with reliable hole mobility of 1 cm2 V-1 s 1 [6], with mobility > 3 cm2 V-1 s-1 reported for thin-film devices on polymer gate dielectrics [9]. For transistors fabricated on single crystals of pentacene, the measured mobility approaches 60 cm2 V-1 s 1 [10]. 

H. E. Katz, C. Kloc, Z. Bao, J. Zaumseil, and V. Sundae, Field-effect transistors made from macroscopic single crystals of tetracene and related semiconductors on polymer dielectrics , Journal of Materials Research 19, 1995 (2004). 

Fig. 2.19. (a) Scheme of a transparent field effect transistor based on ZnO [191]. The gate electrode consists of tin-doped indium oxide (ITO) and the gate dielectric is a multilayer of AECE/TiCE (ATO). (b) Output characteristics (drain-source current as a function of the drain-source voltage) for different gate voltages. The saturation current is about 530 rA at a gate bias of 40 V. From this output characteristics a threshold voltage of 19 V and a field-effect mobility of 27 cm2 V-1 s-1 were calculated [192]... 

G. Nunes Jr., S.G. Zane, J.S. Methb, Styrenic polymers as gate dielectrics for pentacene field-effect transistors,./. Appl. Phys. 98 (2005) 104503. 

A schematic view of a microdielectrometer sensor is shown in Fig. 8 and illustrates the electrode array, the field-effect transistors and a silicon diode temperature indicator 15) which functions as a moderate accuracy ( 2 °C) thermometer between room temperature and 250 °C. The sensor is used either by placing a small sample of resin over the electrodes, or by embedding the sensor in a reaction vessel or laminate. Since all dielectric and conductivity properties are temperature dependent, the ability to make a temperature measurement at the same point as the dielectric measurement is a useful feature of this technique. 

Fig. 6.32. Time dependence of the induced defect density near the dielectric interface of a field effect transistor after the application of a gate bias. The measurement is of the threshold shift, AK, which is proportional to the defect density (Jackson and Moyer 1988).

The other interesting material for electronics is carbon nanotubes. We have shown the application of individual single-walled carbon nanotubes for field effect transistors (FETs) [3]. Carbon nanotubes (CNT) or CNT bundles can be placed between two carbon electrodes playing the role of source and drain. The gate electrode can be made of thin metal stripe under the dielectric film in the region between source and drain. 

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