The area of contact between two semiconductor materials having
different electrical properties, or between a semiconductor and a metal.
Junctions play a fundamental role in semiconductor devices. The most frequently
used is the p-n junction, which is formed between n-type
and p-type semiconductors. A p-n junction has rectifying properties as a result
of the potential barrier built up across the junction by the diffusion of
electrons from the n-type to the p-type material.