Answer to Question #85751 in Electric Circuits for Sun

Question

Explaiin the effect of doping on the energy band diagram of a semiconductor.

Answer 1

The energy diagram basically shows how far some important levels are separated from each other, for example Fermi level, valence band, impurity energy level and so on. Doping thus influences the "distance" between these bands: for example, silicon has 4 valence electrons in its outer shell. By adding a doping atom with 5 valence electrons the semiconductor becomes an n-type semiconductor with one trumping electron, and the "distance" between the donating band and the conduction band shortens. Adding an electron acceptor with 3 electrons on the outer shell creates states near the valence level, and there is hole conduction in the semiconductor.