Semiconductor device

The electrical conductivity and electron mobility for aluminum are 3.8 X 10 (il-m) and 0.0012 m A/ -s, respectively. Calculate the HaU voltage for an aluminum specimen that is 15 mm thick for a current of 25 A and a magnetic field of 0.6 tesla (imposed in a direction perpendicular to the current). 

The HaU voltage may be determined using Equation 18.18. However, it is first necessary to compute the Hall coefficient (1 h) from Equation 18.20b as 

The unique electrical properties of semiconductors permit their use in devices to perform specific electronic functions. Diodes and transistors, which have replaced old-fashioned vacuum tubes, are two familiar examples. Advantages of semiconductor devices (sometimes termed solid-state devices) include small size, low power consumption, and no warmup time. Vast numbers of extremely small circuits, each consisting of numerous electronic devices, may be incorporated onto a small silicon chip. The invention of semiconductor devices, which has given rise to miniaturized circuitry, is responsible for the advent and extremely rapid growth of a host of new industries in the past few years. 

Transistors, which are extremely important semiconducting devices in today s microelectronic circuitry, are capable of two primary types of function. First, they can perform the same operation as their vacuum-tnbe precursor, the triode—that is, they can amplify an electrical signal. In addition, they serve as switching devices in computers for the processing and storage of information. The two major types are the junction (or bimodal) transistor and the metid-oxide-semiconductor field-effect transistor (abbreviated as MOSFET). 

The jimction transistor is composed of two p-n junctions arranged back to back in either the n-p-n or the p-n-p configmation the latter variety is discussed here. Rgme 18.24 is a schematic representation of a p-n-p jimction transistor along with its attendant drcuitry. A very thin n-type base region is sandwiched between p-type emitter and collector regions. The circuit that includes the emitter-base junction (junction 1) is forward biased, whereas a reverse bias voltage is applied across the base-collector junction (junction 2). 

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Cooke M J 1990 Semiconductor Devices (New York Prentice-Hall) p 181... 

Interest in AIN, GaN, InN and their alloys for device applications as blue light-emitting diodes and blue lasers has recently opened up new areas of high-pressure synthesis. Near atmospheric pressure, GaN and InN are nnstable with respect to decomposition to the elements far below the temperatures where they might melt. Thus, large boules of these materials typically used to make semiconductor devices caimot be grown from the... 

The history of semiconductor devices can be traced back to tire paper of Braun, published in 1874, describing rectifying behavior of a contact [1], However, for many years semiconductors were considered too difficult a subject and tire science of semiconductors began only during World War IT... 

Grove A S 1967 Physics and Technology of Semiconductor Devices (New York Wiley)... 

Silicon is prepared commercially by heating silica and carbon in an electric furnace, using carbon electrodes. Several other methods can be used for preparing the element. Amorphous silicon can be prepared as a brown powder, which can be easily melted or vaporized. The Gzochralski process is commonly used to produce single crystals of silicon used for solid-state or semiconductor devices. Hyperpure silicon can be prepared by the thermal decomposition of ultra-pure trichlorosilane in a hydrogen atmosphere, and by a vacuum float zone process. 

Oxygen. High purity oxygen for use in semiconductor device manufacture is produced in relatively small quantities compared to nitrogen. There are two different purification processes in general use for manufacturing the gas distillation and chemical conversion plus adsorption. 

TaF has been characterized by ir, Raman, x-ray diffraction, and mass spectrometry (3,11,12). TaF has been used as a superacid catalyst for the conversion of CH to gasoline-range hydrocarbons (qv) (12) in the manufacture of fluoride glass and fluoride glass optical fiber preforms (13), and incorporated in semiconductor devices (14). TaF is also a catalyst for the Hquid-phase addition of HF to polychlorinated ethenes (15). The chemistry of TaF has been reviewed (1,16—19). Total commercial production for TaF is thought to be no more than a few hundred kilograms aimuaHy. 

Uses. The chemical inertness, thermal stability, low toxicity, and nonflammability of PFCs coupled with their unusual physical properties suggest many useflil applications. However, the high cost of raw materials and manufacture has limited commercial production to a few, small-volume products. Carbon tetrafluoride and hexafluoroethane are used for plasma, ion-beam, or sputter etching of semiconductor devices (17) (see loN implantation). Hexafluoroethane and octafluoropropane have some applications as dielectric gases, and perfluorocyclobutane is used in minor amounts as a dielectric fluid. Perfluoro-1,3-dimethyl cyclohexane is used as an inert, immersion coolant for electronic equipment, and perfluoro-2-methyldecatin is used for... 

The supplanting of germanium-based semiconductor devices by shicon devices has almost eliminated the use of indium in the related ahoy junction (see Semiconductors). Indium, however, is finding increased use in III—V compound semiconductors such as indium phosphide [22398-80-7] for laser diodes used in fiber optic communication systems (see Electronic materials Fiber optics Light generation). Other important indium-containing semiconductors include indium arsenide [1303-11-3] indium antimonide [1312-41 -0] and copper—indium—diselenide [12018-95-0]. 

R. M. Osgood, S. R. J. Bmeck, and H. R. Schlossberg, eds.. Laser Diagnostics and Photochemical Processingfor Semiconductor Devices, North-HoUand, New York, 1983. 

Light-emitting diodes are the most commercially important compound semiconductor devices in terms of both doUar and volume sales. The 1991 worldwide compound semiconductor device market totaled 2.8 biUion (39). Light-emitting diodes accounted for ca 1.9 biUion of this market. Visible and ir LEDs represented 37 and 30%, respectively. These markets are expected to grow as LEDs are increasingly employed in advanced appHcations. 

M. Shur, Physics of Semiconductor Devices Prentice Hall, Englewood Chffs, N.J., 1990. 

E. H. Pudey, "Lead Sulphide, Selenide and TeUuride," ia C. A. Hogarth, ed.. Materials Used in Semiconductor Devices, Wiley-Interscience, New York, 1965. 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toU producers is often economically viable despite high cost, especially for aerospace and microelectronic appHcations. For the majority of iudustrial appHcations, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement iu some appHcations such as multilayer thermal iusulation blankets for satellites and protective coatings for solar cells and other space components (93). For iutedayer dielectric appHcations iu semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors usediu those devices (94). 

Protein Computers. The membrane protein bacteriorhodopsin holds great promise as a memory component in future computers. This protein has the property of adopting different states in response to varying optical wavelengths. Its transition rates are very rapid. Bacteriorhodopsin could be used both in the processor and storage, making a computer smaller, faster, and more economical than semiconductor devices (34). 

Electrically Functional. Refractory coatings are used in semiconductor devices, capacitors, resistors, magnetic tape, disk memories, superconductors, solar ceUs, and diffusion barriers to impurity contamination from the substrate to the active layer. 

The high purity required of sificon and the small size of semiconductor devices place stringent limits on the chemicals used in processing sificon. By far the most important chemical is water which is used extensively to dilute etchants and clean wafers. Pure water (24) is required to have fewer than 0.025... 

A/. This frequendy occurs because semiconductor devices are... 

Semiconductor devices ate affected by three kinds of noise. Thermal or Johnson noise is a consequence of the equihbtium between a resistance and its surrounding radiation field. It results in a mean-square noise voltage which is proportional to resistance and temperature. Shot noise, which is the principal noise component in most semiconductor devices, is caused by the random passage of individual electrons through a semiconductor junction. Thermal and shot noise ate both called white noise since their noise power is frequency-independent at low and intermediate frequencies. This is unlike flicker or ///noise which is most troublesome at lower frequencies because its noise power is approximately proportional to /// In MOSFETs there is a strong correlation between ///noise and the charging and discharging of surface states or traps. Nevertheless, the universal nature of ///noise in various materials and at phase transitions is not well understood. 

A. S. Grove, Phjsics and Technology of Semiconductor Devices ]ohn. Wiley Sons, Inc., New York, 1967. 

B. J. Baliga, Physics of Pomr Semiconductor Devices, PWS Publishing Co., Boston, Mass., 1995. 

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