Degenerate semiconductor

A degenerate semiconductor is a semiconductor that is doped so strong ( or contaminated ) is that it conducts electricity as well as metals. By the impurity moves the Fermi level closer to the conduction band or lies in the band gap is very small or disappears (English band-gap narrowing or gap- shift). Can be explained by the effect of the shielding of the lattice potential introduced by the addition, the free charge carriers. The occupation probabilities in the conduction and valence bands can no longer be described by the Boltzmann statistics.

Silicon and germanium were before 1940 not very pure available (with silicon prior knowledge of the zone melting method ), which is why they have been classified historically as metals due to this fact.