Doping of semiconductors

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n doping This involves substituting Si by neighboring elements that contribute excess electrons. For example, small amounts of P or As can substitute Si.
Since P/As have 5 valence electrons, they behave like Si plus an extra electron. This extra electron contributes to electrical conductivity, and with a sufficiently
large number of such dopant atoms, the material can displays metallic conductivity. With smaller amounts, one has extrinsic n-type semiconduction.
Rather than n and p being equal, the n electrons from the donor usually totally outweigh the intrinsic n and p type carriers so that:


Semiconductor devices
The p − n junction is formed when the two different sides of semiconductor are doped, respectively with holes (for example, Al for Si) and electrons (for
example, P for Si). One of the properties of the p − n junction is that it rectifies — it allows an electric current to pass only in one direction