Depletion region

A region near a semiconductor junction depleted of mobile charge carriers, leaving fixed ionized dopants. Their charge creates an internal electric field and a potential barrier.

PN junction: A semiconductor interface between p-type and n-type regions, forming a rectifying boundary. The depletion region forms where these differently doped regions meet.
Semiconductor: A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled. Its controllable carrier population makes a depletion region possible.
Zener diode: A diode designed to operate in reverse breakdown at a specified voltage. Its heavily doped junction has a narrow depletion region that enables tunneling breakdown.
Forward bias: A voltage polarity across a semiconductor junction that lowers its potential barrier and promotes carrier injection. It narrows the depletion region, unlike reverse bias.
Built-in potential: The equilibrium voltage across a semiconductor junction created by charge separation. The electric field across the depletion region produces this potential barrier.
Doping (semiconductor): The deliberate addition of impurities to a semiconductor to change its carrier concentration. Dopant concentration sets the fixed charge density within the depleted region.
Avalanche breakdown: A reverse-bias failure mechanism in which accelerated carriers create additional carriers by impact ionization. A strong field across the depletion region accelerates carriers to ionizing energies.
Reverse bias: A voltage polarity across a semiconductor junction that raises its barrier and suppresses carrier injection. It widens the depletion region and strengthens its field.
Drift current: Electric-field-driven motion of charge carriers in a material. The depletion-region field drives carriers in the direction opposing diffusion.
Donor (semiconductor): An impurity that contributes an electron to a semiconductor's conduction band. Ionized donors remain positively charged on the n-type side of the region.

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