Bipolar Junction Transistors

Although Bardeen and Brattain's invention of the point-contact transistor came first, it was the bipolar junction transistor conceived by Shockley a month later that really made these electron devices a commercial reality. In January 1948 he had the key insight of "minority carrier injection" - that electrons and holes can briefly coexist in the bulk semiconductor material and flow in the intimate presence of one another. In July 1949 Shockley published his ideas in an article, “The Theory of P-N Junctions in Semiconductors and P-N Junction Transistors”. He further elaborated these ideas in his 1950 book “Electrons and Holes in Semiconductors”, which became the bible of the new field read by thousands of practitioners.

Important advances in materials science helped get junction transistors out of the laboratory and into production. William Pfann's invention of zone refining at Bell Labs provided ultrapure germanium samples with impurity levels of less than a part per billion. Meanwhile, chemist Gordon Teal perfected a technique for growing large single crystals of germanium; he and Morgan Sparks then figured out how to introduce small impurities into the melt and form pn junctions as well as three-layer structures directly in the resulting crystals. Announced in July 1951, such "grown-junction" transistors were used in hearing aids and radios by the mid-1950s. Texas Instruments manufactured the germanium transistors used in the first transistor radio, the Regency TR1, which reached customers by Christmas 1954.

Another approach to making junction transistors had been invented by John Saby at General Electric laboratories in Schenectady, New York, and developed for mass production by RCA. In 1951, he fabricated the so-called alloy-junction transistor by melting pellets of indium on the opposite sides of a thin slab of germanium; the molten indium alloyed with the germanium to form two pn -junctions astride a narrow intervening layer of n-type germanium. Alloy-junction transistors proved easier to manufacture than the grown-junction variety and many transistor producers, large and small, adopted this approach rather than set up elaborate crystal-growing equipment. Philco, for example, made high-frequency alloy-junction transistors by narrowing their base layers as much as technically possible at the time.

One serendipitous outgrowth of these transistor-fabrication efforts came at SONY, which began selling transistor radios in 1955. In 1957, while experimenting on heavily doped germanium pn junctions as part of efforts to reach high frequencies above 100 MHz, Leo Esaki invented the tunnel diode; he observed that some of the electrons were actually traversing the barrier due to quantum-mechanical tunneling. He shared the 1973 Nobel Prize in physics for this fundamental scientific discovery.

Meanwhile, researchers at Bell Labs and other institutions had begun to recognize the limitations of germanium and were turning to silicon as the element of choice for transistors and other semiconductor devices. Being much more difficult to purify due to its higher melting temperature and great reactivity, silicon has a significantly larger gap between its valence and conduction bands. This higher band gap means that silicon transistors are far less sensitive to temperature changes, their leakage currents being far lower than for germanium devices.

Having joined Texas Instruments in 1953, Gordon Teal zealously pursued the quest of making silicon transistors. Before leaving Bell Labs, he had adapted his crystal-growing techniques to work with silicon; at TI he hired physical chemist Willis Adcock to lead a group aimed at developing silicon transistors. In April 1954 they succeeded in making a grown-junction transistor using high-purity silicon. Although Morris Tanenbaum also fabricated silicon transistors at Bell Labs that same year, the TI devices were the first silicon transistors to reach market.

The knotty problem of purifying the silicon was finally solved by Bell Labs metallurgist Henry Theurer, who developed the float-zone refining technique in 1955. This breakthrough and the fabrication of pn junctions by impurity diffusion were the technological advances that pushed the doors open wide for silicon semiconductor devices. By the end of the 1950s, germanium was in decline.

Exercise 5

Find in the text synonyms for the following words.

Thoughts, manufacture, in the meantime, to improve, a plate, to apply, to work out, to start, organisation, complicated, really, to manage, to employ, to head, to produce, to get to, less, highly, apparatus, to create, methods, doping, to finish.

Exercise 6

Make up 10 questions to the text beginning with “When”.

LESSON 11

Exercise 1

Translate the following words paying attention to word-building affixes.

Inexpensive, expense, expensive, expensively, require, requirements, required, requiring, inhabit, uninhabited, inhabitant, emerge, emergence, emergency, re-emerge, emergent, emerged, emerging, diffusion, non-diffusing, diffuse, diffused, diffusible, diffusive, amplify, amplification, amplifier, amplified, amplifying, protection, protective, protect, protector, unprotected, protectorship, protecting, apply, application, applying, applied, misapply, misapplication, appliance, applicant, applicable.

Exercise 2

Translate the following paying attention to modals and their equivalents.

1. Like cable network providers before them, wireless network providers will not have to create the new services themselves. 2. A few years from now, you may be replacing your current DVD player with one that will record an entire high-definition movie on a single disk, which means a capacity of about 25GB, or more than five times that of today’s 4.7GB DVDs. 3. The specification is to be completed in a few month, and licensing will begin. 4. The challenge they have to meet is to establish communication links with signal-to-noise ratios high enough to support broadband communications with easily installed, preferably indoor, antennas. 5. Small wonder, then, that this sort of technology could not even be considered for commercial application until cheap and powerful signal processors became available. 6. It’s surprising to realize that buyers of IP blocks used in SOC devices may not be entirely aware of what they’re getting and how it works. 7.SOC providers could shorten their time to market considerably if they didn’t have to spend up to 70 percent of it verifying that their designs will plug and play. 8. When RTL code is fed into a design verification program, the program can check to determine whether the block behaves as it should. 9. But Deutsche Telecom may have some reorganising to do itself. 10. For a start, engineers could rework the architecture of chips and boards to shorten the distances over which signals have to travel. 11. This may not solve all the industry’s problems, but it’s a step in the right direction. 12.Intel can move data at 10 GHz over a copper wire on the board and should be able to push it to at least 20 GHz. 13. If disk drives were enabled to perform a host of tasks that have traditionally been the work of CPUs, dramatic low-cost improvements could be made in computing environments ranging from laptops to storage networks. 14.Adding intelligent drive features may require changing the standards, and may also require changes in operating system and application software. 15. The only universal rule is: when checking any hf devices, one should make the connection between tester and tested as short as possible. 16.If the range is to be tuned, the equivalent resistance of the crystal and tuning network at the new series-resonant frequency should be found. 17. A single 3.5-inch disk that can hold a few feature-length films today could have the capacity to hold a personal library of a thousand films if the computer storage industry achieves terabit-per-square-inch densities.

Exercise 3

Match Ukrainian translations to the following English phrases.

1. selenium photocells	1. застосування у вiддалених мiсцях
2. light meters	2. космiчнi супутники
3. trace impurities	3. аварiйнi придорожнi телефони
4. manufacturing costs	4. оксидне маскування
5. competitive	5. мiкродомiшки
6. remote applications	6. витравлювати складнi схеми
7. electric-power grid	7. конкурентоспроможний
8. space satellites	8. лiчильники свiтла
9. emergency roadside telephones	9. процес виготовлення
10. an order of	10. електричнi мережi
11. oxide masking at	11. прорив
12. etch intricate patterns	12. селеновi фотоелементи
13. breakthrough	13. на порядок
14. manufacturing process	14. виробничi видатки

Exercise 4

Pay attention to translation of the following phrases.

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