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Unit IX. Semiconductor MaterialsA Semiconductor device is an electronic 1. _____ component made from a material that is neither a good conductor nor a good 2. _______. Such devices have found wide applications because of their compactness, reliability, and low cost. As discrete components, they have found use in power devices, optical sensors, and light emitters, including solid-state lasers. They have a wide range of current- and voltage-handling capabilities, with current ratings from a few nanoamperes (10 −9 ampere) to more than 5,000 amperes and voltage ratings extending above 100,000 volts. More importantly, semiconductor devices lend themselves to integration into complex but readily manufacturable microelectronic circuits. They are, and will be in the foreseeable future, the key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment. A. ____________ Solid-state materials are commonly grouped into three classes: insulators, semiconductors, and conductors. Conductivity or specific conductance is the 3. ______ quantity, and measures a material's ability to conduct an electric 4. _____. Insulators, such as fused quartz and glass, have very low conductivities, on the order of 10 −18 to 10 −10 siemens per centimetre; and conductors, such as aluminum, have high conductivities, typically from 10 4 to 10 6 siemens per centimetre. The conductivities of semiconductors are between these extremes. E __________________________Prior to the invention of the bipolar transistor in 1947, semiconductors were used only as two-terminal 8. ______, such as rectifiers and photodiodes. During the early 1950s, germanium was the major semiconductor material. However, it proved unsuitable for many applications, because devices made of the material exhibited high leakage currents at only moderately elevated temperatures. Since the early 1960s, silicon has become a practical substitute, virtually supplanting germanium as a material for semiconductor 9. ______. The main reasons for this are twofold: (1) silicon devices exhibit much lower leakage currents, and (2) high-quality silicon dioxide (SiO 2), which is an insulator, is easy to produce. Silicon technology is now by far the most advanced among all semiconductor technologies, and silicon-based devices constitute more than 95 percent of all semiconductor hardware sold worldwide. Many of the compound semiconductors have electrical and optical properties that are 10. _____ in silicon. These semiconductors, especially gallium arsenide, are used mainly for high-speed and optoelectronic applications. I. Fill in the gaps with the following terms: ternary, insulator, current, absent, sensitive, circuit, elemental, fabrication, devices, reciprocal. II. Explain the following: Solid-state materials, insulators, conductors, conductivity, voltage, compound semiconductors, ternary compounds, photodiodes, rectifiers, silicon-based. III. Think of the possible title for each paragraph (A – E). IV. Answer the questions: - What is the role of semiconductors in today's technology? - Why do we call conductivity a reciprocal quantity? - What are the elements that semiconductors are composed of? - What elements form ternary compounds? - Can you speak about the development of semiconductor technologies? - What are the advantages of silicon? What are its drawbacks? V. Give a small oral report on semiconductors and semiconductor materials. Date: 2015-01-02; view: 1676
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