Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
Intrinsic Carrier Concentration
Derivation, Limitations
In an intrinsic semiconductor, the number of electrons in conduction band is equal to the number of holes in valence band.
INTRINSIC CARRIER CONCENTRATION
In
an intrinsic semiconductor, the number of electrons in conduction band is equal
to the number of holes in valence band.
In
general, intrinsic carrier concentration ni is equal to electrons
concentration in conduction band (n) or holes concentration in valence band
(p).
Substituting
the expressions of n and p in eqn (2), we have
Taking
square root on both sides in eqn (3), we have
The
eqn (4) is expression for intrinsic carrier concentration
Limitations of intrinsic semiconductor
Intrinsic
semiconductors cannot be directly used to fabricate devices due to the
following limitations:
i.
Electrical conductivity is low. Germanium has a conductivity of 1.67 Ω-1
m-1 which is nearly 107 times smaller than that of
copper.
ii.
Electrical conductivity is a function of temperature and increases exponentially
as temperature increases.
In intrinsic or pure semiconductors, the carrier concentration of both electrons and holes is very low at normal temperatures.
In
order to get sufficient current density through semiconductor, a large
electrical field should be applied. This problem is overcome by adding suitable
impurities into intrinsic semiconductors.
Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics : Tag: : Derivation, Limitations - Intrinsic Carrier Concentration
Physics for Electronics Engineering: Unit III: Semiconductors and Transport Physics
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Physics for Electronics Engineering
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