In a p-type semiconductor, the concentration of holes in the valence band is higher than the concentration of free electrons in the conduction band. This is because the p-type semiconductor has been doped with impurities that introduce positively charged holes into the crystal lattice.

Let Ea be the concentration of acceptor level and Na be the concentration of acceptor atoms. Then concentration of ionized acceptor (Na-) = f (ε)Na. Here f(ε) = F-D distribution for electron.

If Ev be energy of valance band edge and m_h the effective mass of electron. Then concentration of electrons in the conduction band

Let n be the concentration of electrons in the conduction band. Then

At T = 0k, Ef lies between the top of the donor level and the bottom of the conduction band. As the temperature is increased, Ef drops and approaches towards the centre of forbidden gap at extremely high temperature thereby rendering n type semiconductor on intrinsic semiconductor.

Substituting equation 3 in equation 2 we get

is acceptor ionization energy.

Equation 4 gives the concentration of holes in the valance band of p type semiconductor.

The concentration of holes in the valence band of a p-type semiconductor can be controlled by adjusting the amount of doping impurities added to the semiconductor. The higher the concentration of impurities, the higher the concentration of holes in the valence band, and the better the semiconductor will be for certain electronic applications.

This note is a part of the Physics Repository.

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