In
semiconductor physics, an acceptor is a
dopant
A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. When ...
atom that when substituted into a
semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...
lattice forms a
p-type region.
When
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...
(Si), having four
valence electron
In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair form ...
s, is doped with elements from
group III of the
periodic table, such as
boron (B) and
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
(Al), both having three valence electrons, a
p-type semiconductor is formed. These dopant elements represent ''trivalent impurities''. Other trivalent dopants include
indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts ...
(In) and
gallium (Ga).
When substituting for a silicon atom in the
crystal lattice, the three valence electrons of boron form
covalent bonds with three of the Si neighbours but the bond with the fourth remains unsatisfied. The initially electro-neutral acceptor becomes negatively charged (
ionised).
The unsatisfied bond attracts electrons from the neighbouring bonds. At
room temperature, an electron from a neighbouring bond can jump to repair the unsatisfied bond thus leaving an
electron hole
In physics, chemistry, and electronic engineering, an electron hole (often simply called a hole) is a quasiparticle which is the lack of an electron at a position where one could exist in an atom or atomic lattice. Since in a normal atom or ...
, which is a place where an electron is deficient. The hole, being positively charged, attracts another electron from a neighbouring bond to repair this unsatisfied bond. This chain-like process results in the hole moving around the crystal as a
charge carrier. This process can sustain in an
electric current useful in
electronic circuits.
See also
*
Donor (semiconductors) In semiconductor physics, a donor is a dopant atom that, when added to a semiconductor, can form a n-type region.
For example, when silicon (Si), having four valence electrons, is to be doped as a n-type semiconductor, elements from group V lik ...
*
Electron acceptor
*
Semiconductors
References
Semiconductor properties
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