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Doping of a pure silicon array. Silicon based intrinsic semiconductor becomes extrinsic when impurities such as boron and antimony are introduced.. In semiconductor production, doping is the intentional introduction of impurities into an intrinsic (undoped) semiconductor for the purpose of modulating its electrical, optical and structural properties.
For example, doping pure silicon with a small amount of phosphorus will increase the carrier density of electrons, n. Then, since n > p, the doped silicon will be a n-type extrinsic semiconductor. Doping pure silicon with a small amount of boron will increase the carrier density of holes, so then p > n, and it will be a p-type extrinsic ...
While there is considerable scatter in the experimental data, for noncompensated material (no counter doping) for heavily doped substrates (i.e. and up), the mobility in silicon is often characterized by the empirical relationship: [37] = + + where N is the doping concentration (either N D or N A), and N ref and α are fitting parameters.
The effect occurs when the electron carrier concentration exceeds the conduction band edge density of states, which corresponds to degenerate doping in semiconductors. In nominally doped semiconductors, the Fermi level lies between the conduction and valence bands. For example, in n-doped semiconductor, as the doping concentration is increased ...
Silicon wafers are generally not 100% pure silicon, but are instead formed with an initial impurity doping concentration between 10 13 and 10 16 atoms per cm 3 of boron, phosphorus, arsenic, or antimony which is added to the melt and defines the wafer as either bulk n-type or p-type. [27]
Using the carrier concentration equations given above, the mass action law can be stated as = =, where E g is the band gap energy given by E g = E c − E v. The above equation holds true even for lightly doped extrinsic semiconductors as the product n p {\displaystyle np} is independent of doping concentration.
Phosphorus atom acting as a donor in the simplified 2D silicon lattice. For example, when silicon (Si), having four valence electrons, is to be doped as a n-type semiconductor, elements from group V like phosphorus (P) or arsenic (As) can be used because they have five valence electrons. A dopant with five valence electrons is also called a ...
A degenerate semiconductor is a semiconductor with such a high level of doping that the material starts to act more like a metal than a semiconductor. Unlike non-degenerate semiconductors, these kinds of semiconductor do not obey the law of mass action, which relates intrinsic carrier concentration with temperature and bandgap.