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No description available.

No description available.

No description available.

No description available.

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No description available.

Accurate small and large-signal models of metal-semiconductor field effect transistor (MESFET) devices are essential in all modern microwave and millimeter wave applications. Those models are used for robust designs and fabrication development. The sophistication of modern communication systems urged the need of monolithic microwave integrated circuits (MMICs), which consists of many MESFETs on the same chip. As the chip density increases, the need of accurate MESFET models becomes more pronounced. In this study, a new technique has been developed to extract a 15-element small signal model of MESFET devices. This technique implies the use of three sets of S-parameter measurements at different bias conditions. The technique consists of two major steps; in the first step, some of the bias-independent extrinsic parameters are estimated in preparation for the second step. In the second step, all other parameters should be extracted at the bias point of interest. This technique shows reliable results. Unlike other optimization techniques, our proposed technique shows insensitivity to the unavoidable measurement errors over any frequency range. It shows a unique solution for all parameter values. This technique has been tested on S-parameters of a hypothetical device model and compared with other optimization-based extraction techniques. Moreover, it has been also applied to GaAsTEK 0.8x300 μm2 MESFETs to extract the model parameters at different bias voltages. The study reveals accurate and consistent results among the similar devices on the same wafer. Some thermal characteristics of the small-signal parameters are discussed. The parameters are extracted from measurements at three temperatures for two similar devices on the same wafer. The thermal results of the two devices demonstrate consistent results, which assure the preciseness, and robustness of our proposed technique. In addition, the relation between the small-signal model parameters and the large signal model parameters is also presented. The parameters of an empirical model for the drain-source current are extracted from the dc measurements along with the small-signal transconductance and output conductance. The large-signal model results for a GaAsTEK 0.8x300 μm2 MESFET are introduced. / Ph. D.

This dissertation will outline solution processable materials and fabrication techniques to manufacture flexible electronic devices from them. Conductive ink formulations and inkjet printing of gold and silver on plastic substrates were examined. Line patterning and mask printing methods were also investigated as a means of selective metal deposition on various flexible substrate materials. These solution-based manufacturing methods provided deposition of silver, gold and copper with a controlled spatial resolution and a very high electrical conductivity. All of these procedures not only reduce fabrication cost but also eliminate the time-consuming production steps to make basic electronic circuit components. Solution processable semiconductor materials and their composite films were also studied in this research. Electrically conductive, ductile, thermally and mechanically stable composite films of polyaniline and sulfonated poly (arylene ether sulfone) were introduced. A simple chemical route was followed to prepare composite films. The electrical conductivity of the films was controlled by changing the weight percent of conductive filler. Temperature dependent DC conductivity studies showed that the Mott three dimensional hopping mechanism can be used to explain the conduction mechanism in composite films. A molecular interaction between polyaniline and sulfonated poly (arylene ether sulfone) has been proven by Fourier Transform Infrared Spectroscopy and thermogravimetric analysis. Inkjet printing and line patterning methods also have been used to fabricate polymer resistors and field effect transistors on flexible substrates from poly-3-4-ethyleneoxythiophene/poly-4-sytrensulfonate. Ethylene glycol treatment enhanced the conductivity of line patterned and inkjet printed polymer thin films about 900 and 350 times, respectively. Polymer field effect transistors showed the characteristics of traditional p-type transistors. Inkjet printing technology provided the transfer of semiconductor polymer on to flexible substrates including paper, with high resolution in just seconds. / Ph. D.