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By Alaina G. Levine
On December 14, 2006, the American Physical Society presented a plaque to Bell Laboratories in honor of John Bardeen (1908-1991), William B. Shockley (1910-1989), and Walter H. Brattain (1902-1987) for their invention of the transistor, which has been called “the most important invention of the 20th Century.”1 Developed from semiconductor material, the transistor was the first device that could both amplify an electrical signal, as well as turn it on and off, allowing current to flow or to be blocked.2 It was small in size, generated very low heat, and was very dependable, making possible a breakthrough in the miniaturization of complex circuitry.3 The transistor heralded in the “Information Age” and paved the way for the development of almost every electronic device, from radios to computers to space shuttles. For their monumental “researches on semiconductors and their discovery of the transistor effect,"4 Bardeen, Shockley and Brattain were presented with the Nobel Prize in Physics in 1956.
The genesis of the transistor emanates, interestingly enough, from a marketing problem. In the early part of the 20th Century, AT&T was engrossed in expanding its telephone service across the continent in an effort to beat the competition. The company turned to its research and development arm, Bell Laboratories, to develop innovations to meet this need.
At the time, telephone technology was based on vacuum tubes, which were essentially modified light bulbs that controlled electron flow, allowing for current to be amplified. But vacuum tubes were not very reliable, and they consumed too much power and produced too much heat to be practical for AT&T’s needs. Furthermore, as scientists at Bell Labs discovered, transcontinental telephone communication required the use of ultrahigh frequency waves and the vacuum tubes were incapable of picking up rapid vibrations.5
An all-star team of scientists was assembled at Bell Labs to develop a replacement for the vacuum tubes based on solid-state semiconductor materials.6 Shockley, who had received his Ph.D. in physics from the Massachusetts Institute of Technology in 1936 and joined Bell Labs the same year, was selected as the team leader. He recruited several scientists for the project, including Brattain and Bardeen.
Walter Brattain had been working for Bell Labs since 1929, the year he received his Ph.D. in physics from the University of Minnesota. His main research interest was on the surface properties of solids.7 John Bardeen was a theoretical physicist with an industrial engineering background. With a Ph.D. in physics from Princeton University, he was working as an assistant professor at the University of Minnesota when Shockley invited him to join the group.8
The team commenced work on a new means of current amplification. In 1945, Shockley designed what he hoped would be the first semiconductor amplifier, an apparatus that consisted of “a small cylinder coated thinly with silicon, mounted close to a small, metal plate”. The device didn't work, and Shockley assigned Bardeen and Brattain to find out why.9
In 1947, during the so-called “Miracle Month” of November 17 to December 23, Brattain and Bardeen performed experiments to determine what was preventing Shockley’s device from amplifying. They noticed that condensation kept forming on the silicon. Could this be the deterrent? Brattain submerged the experiment in water “inadvertently creating the largest amplification thus far.” Bardeen was emboldened by this result, and suggested they modify the experiment to include a [gold] metal point that would be pushed into the silicon surrounded by distilled water. At last there was amplification, but disappointingly, at a trivial level.
But the scientists were galvanized by the meager result, and over the next few weeks, experimented with various materials and set ups. They replaced the silicon with germanium, which resulted in amplification 330 times larger than before. But it only functioned for low frequency currents, whereas phone lines, for example, would need to handle the many complicated frequencies of the human voice10.
Next, they replaced the liquid with a layer of germanium dioxide. When some of the oxide layer accidentally washed away, Brattain continued the experiment shoving the gold point into the germanium and voila! Not only could he still achieve current amplification, but he could do so at all frequencies. The gold contact had put holes in the germanium and the punctures "canceled out the effect of the electrons at the surface, the same way the water had."11 Their invention was finally increasing the current at all frequencies.
Bardeen and Brattain had achieved two special results: the ability to get a large amplification at some frequencies, and a small amplification for all frequencies. Their goal now was to combine the two. The essential components of the device thus far were the germanium and two gold point contacts that were fractions of a millimeter apart. With this in mind, Brattain placed a gold ribbon around a plastic triangle, and cut it through one of the points. When the point of the triangle touched the germanium, electric current entered through one gold contact and increased as it rushed out the other. They had done it – it was the first point-contact transistor. On December 23, Shockley, Bardeen and Brattain presented their “little plastic triangle” to the Bell Labs VIPs and it became official: the super star team had invented the first working solid state amplifier12.
Following the triumph of the transistor, the three amplifying architects went their separate ways. Shockley left Bell Labs in 1955 to become the Director of the Shockley Semi-Conductor Laboratory of Beckman Instruments, Inc. in Mountain View, Ca. His company was one of the first of its kind in Northern California and quickly attracted more semiconductor labs and related computer firms to the area. Soon the region had a new moniker: Silicon Valley.
Bardeen left Bell Labs in 1951 for a professorial appointment in electrical engineering and physics at the University of Illinois. He was named a member of the Center for Advanced Study of the University in 1959. He continued his research in solid state physics and in 1972 shared a second Nobel Prize in physics for the first successful explanation of superconductivity.
Brattain remained at Bell Labs and received various honorary degrees and awards for his work, including being named a Fellow of the APS, the American Academy of Arts and Sciences and the American Association for the Advancement of Science.
Copyright © 2008, Alaina G. Levine