Electrons and Holes in Semiconductors

A semiconductor can generally be treated in a similar way to a free electron solid. The energies corresponding to the permitted bands are first calculated. The levels in each band are then filled with electrons until the supply has been exhausted. As previously defined, the Fermi level is the top-most filled level at zero Kelvin. As in the Free Electron model, it is only those electrons in the vicinity of the Fermi level which are significant in the conduction process. Therefore, our treatment can be restricted to a study of the properties of the highest filled and lowest empty energy bands, which are more commonly known as the valence band and the conduction band .