Esaki, Leo

(1925– ) Japanese physicist: discovered the tunnel (Esaki) diode.

While working for his doctorate on semiconductors at the University of Tokyo (1959), Esaki was also leading a small research group at the Sony Corporation. He chose, in 1957, to investigate conduction by quantum mechanical ‘tunnelling’ of electrons through the potential energy barrier of a germanium p-n diode. Such conduction is in the reverse direction to the normal electron drift and, using narrow junctions (only 100 Å wide) with heavy impurity doping of the p-n junction, Esaki observed the effect. He realized that with narrower junctions the effect would become so strong that the total current would actually fall with increasing bias (negative resistance) and succeeded in making such devices (tunnel or Esaki diodes) in 1960. These devices have very fast speeds of operation, small size, low noise and low power consumption; they have widespread electronic applications in computers and microwave devices. In 1960 Esaki joined IBM’s Thomas J Watson Research Centre and in 1973 was awarded the Nobel Prize with and I Giaever (1929– ) for work on tunnelling effects.