Semiconductor carrier concentration

The most direct effect of doping concentration on semiconductor is its carrier concentration. In thermal equilibrium, an undoped intrinsic semiconductor has an equal concentration of electrons and holes.

As shown in the following formula:

n= p= n where n is the electron concentration in the semiconductor, p is the hole concentration of the semiconductor, and n is the carrier concentration of the intrinsic semiconductor. n will change with different materials or temperatures. For silicon at room temperature, n is about 1×10 cm.

Generally, the higher the doping concentration, the better the conductivity of the semiconductor will become, because the number of electrons that can enter the conduction band will increase with the doping concentration. Semiconductors with very high doping concentrations are widely used in today's integrated circuit processes to replace some metals because their electrical conductivity is close to that of metals. High doping concentrations are usually followed by a superscript "+" sign after n or p, for example, n represents a very high doping concentration of N-type semiconductors, and vice versa, for example, p represents lightly doped P-type semiconductors. In particular, even if the doping concentration is high enough to "degenerate" a semiconductor into a conductor, the concentration of the doping is still very different from the original concentration of semiconductor atoms.

For a silicon semiconductor with a lattice structure, the atomic concentration is about 5×10 cm, and the doping concentration in the general integrated circuit process is about 10 cm to 10 cm. A semiconductor with a doping concentration of more than 10 cm is generally considered a "degenerated semiconductor" at room temperature. In heavily doped semiconductors, the concentration ratio of doping and semiconductor atoms is about one part in a thousand, while light doping may be as high as one part in a billion. In the semiconductor process, the doping concentration is tailored to the needs of the manufactured component to suit the needs of the user.