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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.
Charge carrier density, also known as carrier concentration, denotes the number of charge carriers per volume. In SI units , it is measured in m −3 . As with any density , in principle it can depend on position.
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 pentavalent impurity. [1] Other pentavalent dopants are antimony (Sb) and ...
An extrinsic semiconductor is one that has been doped; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal, which is called an intrinsic semiconductor.
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.
Boron atom acting as an acceptor in the simplified 2D silicon lattice. When silicon (Si), having four valence electrons, is doped with elements from group III of the periodic table, such as boron (B) and aluminium (Al), both having three valence electrons, a p-type semiconductor is formed. These dopant elements represent trivalent impurities.
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.
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.