Impurity (semiconductors)

An impurity is a foreign atom in a semiconductor crystal that changes its electrical properties. Impurities can be deliberately added as dopants or introduced unintentionally during growth and processing.

Doping (semiconductor): The deliberate introduction of impurity atoms into a semiconductor to change its electrical properties. Doping is the controlled use of impurities to set a semiconductor’s carrier concentration.
Semiconductor: A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled. Impurities alter the conductivity of this broader class of materials.
N-type semiconductor: A semiconductor whose majority mobile charge carriers are electrons. Donor impurities create the excess electrons that define n-type material.
Intrinsic semiconductor: A semiconductor with no intentional dopants, whose carriers arise from thermal excitation or intrinsic defects. It provides the baseline for distinguishing impurity-controlled conduction.
Donor (semiconductor): An impurity that supplies an electron to a semiconductor’s conduction band or donor state. Donor impurities provide the extra electrons associated with n-type conductivity.
Crystal lattice: A repeating three-dimensional arrangement of atoms in a crystalline solid. An impurity occupies a lattice site or a space between lattice atoms.
P-type semiconductor: A semiconductor whose majority mobile charge carriers are holes. Acceptor impurities create the excess holes that define p-type material.
Compensation (semiconductors): The reduction of net doping when donor and acceptor impurities coexist in a semiconductor. Opposing impurity types can cancel one another’s electrical contributions.
Acceptor (semiconductor): An impurity that accepts an electron, creating a mobile hole in a semiconductor’s valence band. Acceptor impurities produce the holes associated with p-type conductivity.
Covalent bond: A chemical bond formed when atoms share pairs of electrons. Valence differences between an impurity and host atoms determine donated or missing bonds.

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