A doped semiconductor has had specific atoms, such as boron or phosphorus, introduced into its crystal lattice. These impurities either add free electrons (n-type) or create electron deficits called holes (p-type). Controlling the type and concentration of doping is the fundamental mechanism for creating the junctions that make diodes and transistors function.
The substrate is heavily doped to reduce its series resistance before we grow the epitaxial layer.
Related terms
Junction
The physical interface where two different materials or conductors meet.
Wafer
A highly polished slice of semiconductor material used as the foundation for fabricating integrated circuits.
MOSFET
A metal-oxide-semiconductor field-effect transistor is a voltage-controlled switch used to amplify or switch electronic signals.