Impurities in which impurity atoms replace lattice atoms and are located at lattice points

Impurity atoms are located in the interstitial positions between lattice atoms

Impurity concentration

impurity ionization

impurity ionization energy

donor (donor)

recipient (acceptor)

A donor energy level very close to the bottom of the conduction band or an acceptor energy level very close to the top of the valence band

A donor energy level that is far from the bottom of the conduction band or an acceptor energy level that is far from the top of the valence band

When a semiconductor is doped with donor impurities and acceptor impurities at the same time, the donor impurities and acceptor impurities cancel each other out.

When the donor impurity concentration is similar to the acceptor impurity concentration, the donor electrons are just enough to fill the acceptor energy level, and the impurities cannot provide electrons and holes to the conduction band and valence band.

The net impurity concentration in the semiconductor after impurity compensation has occurred

Isoelectronic impurities are impurity atoms with the same number of valence electrons as the host crystal atoms. After they replace the same group of atoms at the lattice point, they are basically electrically neutral.

After the electron trap captures the carriers, it becomes a charged center. Due to the Coulomb effect, the charged center can capture another carrier of the opposite sign to form a bound exciton.

Ideal crystal: ① Assume that atoms are stationary at the lattice point position of a strictly periodic crystal lattice; ②Pure and free of impurities; ③ Complete crystal structure. actual crystal ① Atoms are not stationary, but vibrate near their equilibrium position; ② Contains some impurities; ③ Various forms of defects exist in crystals.

Point defects: vacancies, interstitial atoms Line Defect: Dislocation Surface defects: stacking faults, grain boundaries in polycrystals

The content is small, the energy level is deep, and multiple energy levels will be generated. The impact on the carrier concentration and conductivity type of the semiconductor is weaker than that of shallow energy level impurities, but the recombination effect of carriers is stronger than that of shallow energy level impurities.

Si replaces the Ga atom in GaAs to act as a donor, and replaces the As atom to act as an acceptor. The electron concentration in the conduction band increases with the increase of Si impurity concentration, and tends to be saturated when the Si impurity concentration increases to a certain level. Si first replaces Ga atoms to play the donor role, and as the Si concentration increases, Si replaces As to play the acceptor role.