Shockley , William Bradford

(1910–1989) British–American physicist

Shockley, born the son of a mining engineer in London, was educated at the California Institute of Technology and at Harvard, where he obtained his PhD in 1936. He started work at the Bell Telephone Laboratories in 1936. In 1963 he took up an appointment as professor of engineering at Stanford University.

Shockley is noted for his early work in the development of the transistor – an invention that has had a profound effect on modern society. He collaborated with John Bardeen and Walter Brattainin their work on the point-contact transistor (1947). The following year Shockley developed the junction transistor.

In semiconductors such as germanium and silicon the electrical conductivity is strongly affected by impurities. The germanium and silicon atoms have four outermost electrons and an impurity such as arsenic, with five outer electrons, contributes extra electrons to the solid. In such materials the current is carried by negative electrons and the conductivity is said to be n-type. Alternatively, impurities such as boron, with three outer electrons, have a different effect in that they introduce ‘holes’ – i.e., ‘missing’ electrons. An electron on an adjacent atom can move to ‘fill’ the hole, leaving another hole. By this mechanism electrical conduction is by movement of positive holes through the solid – the conductivity is said to be p-type.

Shockley experimented with junctions of p- and n-type material, showing how they act as rectifiers. He formed the first junction transistor of a thin layer of p-type material sandwiched between two n-type regions. This n–p–n junction transistor could be used to amplify current. Shockley shared the 1970 Nobel Prize for physics with Bardeen and Brattain.