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Shockley

William Bradford Shockley

Achievements: 1956 Nobel for Physics (with John Bardeen and Walter H. Brattain) for the development of the transistor.

Born: February 13, 1910; London, England

Died: August 12, 1989; Palo Alto, California (Aged  79)

Field & Discipline: Science; Engineering; Physics; Electronic Engineering

Language: English

Father: William Hillman Shockley

Mother: May Bradford

Siblings: None

Spouse: Jean Alberta Bailey (m. 1933-55); Emily I. Lanning (m. 1955)

Children: with Bailey: Alison; William; Richard

Education: Hollywood High School (1922-27); University of California at Los Angeles (UCLA 1927-28); California Institute of Technology (Caltech 1928-32); MIT (1932-36)

Major Work:

“Electrons and Holes in Semi-conductors” (1950 )

Life & Times:

In 1932 Shockley received a Ph.D. in physics in 1936 for his thesis "Calculations of Wave Functions for Electrons in Sodium Chloride Crystals.” This work would become the foundation of his subsequent research.

In 1936, Shockley began working for the Bell Telephone Laboratories in Murray Hill, NJ, where his first project was the design of an electron multiplier, a special kind of vacuum tube that acted as an amplifier.   He soon became involved in solid-state physics research and in 1939 he proposed a radical new approach to the transmission of

electric signals, using solid-state components rather than vacuum tubes.

At that time, vacuum tubes such as the thermionic valve (invented by the English engineer [work related to] John Ambrose Fleming* in 1904), were a core component of communication devices like radios,  to rectifying (creating a unidirectional current) and boosting electronic signals. But their need for power to heat the cathodes, fragility and short-life span were major disadvantages, and throughout the 1930s Bell was looking for alternates.

By 1939, Shockley was experimenting with semi-conducting materials like silicon and germanium (from deposits first discovered by [used materials found by] Maclure* in the early 19th century), which conduct an electrical current far less efficiently than conductors like silver and copper, but more effectively than insulators like glass and most plastics.  

Semi-conductors be made to conduct electricity primarily in only one direction, and so can convert alternating current into direct current. Shockley knew about early work on semi-conductors by [followed up work by] Braun* and [followed up work by] Fritts*, and that one semi-conductor mineral, galena, attached to a "cat's whisker" (coil of wire) had been used as a rectifier of the antenna signals picked up from radio waves in early crystal radio sets.

Building on this basis, his experiments in solid-state physics suggested that semi-conductors might have much wider application in new kinds of communication. In 1945,  after the War, he was able to return to Bell Labs as director of the solid-state physics research programme. 

Together with [won Nobel with] Bardeen* and [won Nobel with] Brattain*, Shockley first tried to simulate the principle of the vacuum tube by applying an electric field across a semi-conductor to control the current flow, but although his calculations had promised that this field effect would produce amplification, the experiment failed.

Bardeen suggested that the applied field of electric current was probably prevented from penetrating the interior of the semi-conductor by electrons trapped in the semi-conductor's surface layers, and this insight led to a series of studies of the surface effects of applied currents.

It was already known that conduction in semi-conductors results from two kinds of charges:-  electrons (those in excess of the number required to maintain the semi-conductor's crystal structure) and "holes" (representing missing electrons which behave as positive charges equalling the negative charges of electrons).

When an electron moves "forwards" in order to fill a hole, it leaves a new hole behind which appears to be moving backwards.  Shockley's calculations revealed that if impurities were introduced into the pure crystal in the form of atoms that did not exactly fit into the regular crystal structure, the number of either excess electrons (the impurity designated n-type) or holes (the impurity designated p-type) was increased.

In 1947 Bardeen and Brittain made the first successful amplifying semi-conductor device, or point contact transistor:  a block of n-type germanium with two closely spaced gold contacts on one side and a broad tungsten electrode contact on the opposite side. To one gold contact (the emitter) a small positive voltage was applied in relation to the broad electrode (the base), and a large negative voltage was applied to the second contact (the collector).

Shockley found that when a voltage was applied to the emitter in series with the base voltage, it was greatly amplified in the collector circuit (the result of the introduction of holes into the germanium by the emitter contact, and the flow of these newly generated holes directly to the collector contact where they increased the current in the collector circuit).

The development of the transistor was first announced in a short article in the “New York Times” on 1 July 1948.

A few months later, Shockley proposed a modification of the point contact transistor which used a thin layer of p-type semi-conductor (in which the charge is carried by holes) sandwiched between two layers of n-type semi-conductor (where the charge is carried by electrons), with all the regions having separate contacts.

When this new “junction transistor” was constructed by Brattain in 1950 (the year Shockley wrote his “Electrons and Holes in Semi-conductors”) it was found to work more efficiently and to be a lot easier to manufacture than the point contact version. Improvements in the techniques for growing, purifying and processing silicon crystals soon followed, and Shockley's idea of a field effect transistor then became realizable,  and it remains the type most widely used in electronic devices today. The junction transistor revolutionized electrons when the transistor principle was applied to silicon chips, and integrated circuits containing thousands of minute transistors were

developed,  making possible the electronic revolution.

Shockley, Bardeen and Brattain were jointly awarded the 1956 Nobel Prize for

Physics for their development of the transistor.

In 1963 Shockley embarked on a new career as the first Alexander M. Poniatoff Professor of Engineering and Applied Science at Stanford University. Here he became interested in genetics and the origins of human intelligence, and, using data taken primarily from U.S. Army pre-induction IQ tests, he developed the highly controversial hypothesis that the genetic component of a person's intelligence was based on racial heritage, and that people of African ancestry were inherently less intelligent than those of

Caucasian ancestry.

He also became convinced that the U.S. population was threatened with a deterioration in mental ability because those of low IQs produced far more children than did those with higher IQs, and ignited further controversy by suggesting that inferior individuals (those with an IQ below 100) be paid to undergo voluntary sterilization.

Assessment:

Oneliner: WB Shockley, Nobel for the transistor

Bibliography:

Attachments