Field effect mobility devices

It is generally well appreciated now that the choice of the right dielectric is crucial for achieving optimum field-effect mobility, device stability and reliability. In the same way as silicon MOS technology owes much to the quality of the Si-Si02 interface, dielectrics for organic FETs have recently received significant attention. 

Figure 14-23. Variation of the field-effect mobility, as deduced by differentiating the drain current at Vt,=-i V, as a function of the gale voltage, for the same device as in Figure 14-22.

Chen, C.-Y. Kanicki, J. 1996. High field-effect-mobility a-Si H TFT based on high deposition rate PECVD materials. IEEE Electron Device Lett. 17 437-439. 

Figure 12.3. Benchmark of peer-reviewed academic reports of organic semiconductor device field-effect mobility versus time of report. All data points are for spin-coated organic semiconducting transistors. Solid points are derived from the benchmark study completed in 2002 by Brazis and Dyrc at Motorola (unpublished). The curve is a calculated estimation, based on these data, of what the expected mobility values will be in the future. The open points are data derived in 2005 from the public journals for verification of the 2002 prediction.6 38... 

Figure 9.7a shows an example of a-Si H TFT transfer characteristics in linear regime with different W/L ratios and an example of a-Si H TFT characteristics in saturation regime with W/L = 170 pm/6 kpm. A threshold voltage (Vth) of 10 = 11 V, a field-effect mobility (p) of 0.2 0.3 cm2/(V s), a subthreshold swing slope of 0.8 dec/V, and a current ON/OFF ratio of larger than 106 for VGS from —10 to 30 V were obtained from these curves for a-Si H TFTs. These devices were used in 4-a-Si H TFTs AM-PLEDs. The electrical properties of a-Si H TFTs used in 3-a-Si H TFTs AM-PLEDs are described in Ref. [18]. 

Digital lithographically processed TFT arrays having 128 x 128 pixel with 75 dpi resolution were fabricated directly on the PEN. Figure 11.15 shows a photograph of the completed flexible array. The I-V transfer and output curves for a typical TFT pixel (W/L x 1) within the array are shown in Fig. 11.16. The device has on/ofF ratios of >108, sub-threshold slopes of 0.5 V decade-1, and field-effect mobility of... 

Figure 12.9 shows the output and transfer characteristics of a state-of-the-art, polymer FET fabricated using the Plastic Logic direct-write manufacturing process (L = 10 pm). No encapsulation of the TFT is present other than what is naturally provided by the presence of the PET substrate on the bottom and an inkjet printed silver gate electrode on the top. The device exhibits a field-effect mobility of 0.04 cm2 V 1 s 1 and ON-OFF current ratio of 5 x 10s. The threshold potential is Vt = 5-6 V. These basic TFT performance values can be achieved consistently in a manufacturing environment, and are sufficient to drive a 100 dpi electronic paper display with A5 size. 

D. J. Gundlach, C.-C. Kuo, S. F. Nelson, T. N. Jackson, Organic thin film transistors with field-effect mobility > 2 cm2 V-1 s 1, presented at 57th Device Research Conference Digest, 1999. 

The temperature dependence of the ON-current and also of the field-effect mobility fi have been studied in a number of optimized devices. Since both these quantities behave in a similar way, we shall concentrate here on the field-effect mobility. 

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