Glossary / Semiconductors
p-n junction
The boundary between n-type semiconductor, rich in electrons, and p-type, rich in holes. It lets current flow in only one direction.
In 1940 Russell Ohl at Bell Labs noticed that shining light on a silicon rod produced a voltage, and traced it to a boundary inside the crystal where the type of impurity changed. That is the p-n junction — also the principle of the solar cell.
In 1949 William Shockley worked out the theory of how current flows across the junction and showed how to build a transistor from it[1]. Diodes, solar cells, LEDs and many transistors rest on the properties of this boundary.
Related terms
- TransistorA semiconductor device in which a small signal controls a larger current, so it can amplify or switch. The basic component of all electronics.
- MOS transistorA transistor built from a metal electrode, an oxide layer and a semiconductor, in which a voltage on the electrode alone opens and closes the channel. Most of today's chips are made of these.