Esaki was born in Osaka, Japan, on March 12, 1925. He attended Tokyo University, where he received his master of science degree in 1947 and his Ph.D. in physics in 1959. His first research was conducted as part of a small research group at the Sony Corporation in Tokyo.

Esaki's primary interest at the time concerned the phenomenon known as tunneling. According to classical physics, a particle that encounters an energy field greater than its own kinetic energy can not pass through that field. The electric resistance of a material can be made great enough, for example, to prevent an electrical current (a flow of electrons) from passing through the material.

The same prohibition does not apply in quantum mechanics. According to quantum theory, particles also have wave properties. These waves have some probability of penetrating an energy barrier that, in classical physics, would seem to prevent their passage. This process...