CoachA dopant is a foreign atom put in a semiconductor on purpose, in small amounts, to provide carriers. In an n-type semiconductor the dopant has one more valence electron than the atom it replaces (phosphorus in silicon) and gives it to the conduction band from a donor level just below that band; in a p-type semiconductor it has one fewer (boron in silicon) and accepts an electron from the valence band into an acceptor level just above it, leaving a hole.
