Intrinsic Semi Conductor Materials

7/25/2019 Intrinsic Semi Conductor Materials

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Intrinsicemi-conductor

Materials


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Introduction

Intrinsic semiconductors aresemiconductors which do not contain

impurities. They do contain electrons as

well as holes. The electron densityequals the hole density since the

thermal activation of an electron from

the valence band to the conduction bandyields a free electron in the conduction

band as well as a free hole in the

valence band.


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Introduction

Intrinsic by denition means natural orinherent, and intrinsic semiconductors

are the bulk properties of the

semiconductor material itself, not thoseof dopants or impurities. Silicon and

germanium are the two most commonly

used eamples of intrinsicsemiconductors, as they are elementalsemiconductors and were some of the

rst widely studied and usedsemiconductors.


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Semiconductor Structure

The electronic structure ofsemiconductors are the foundation of

their unique properties. Themechanisms which make

semiconductors their own class ofmaterial is based on the electricalstructure, which dictates the core

properties of semiconductors.


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The most well known electricconductors are metals. !etals are able

to carry an electric "ow because of

their available free electrons that canpass from one atom to the net. This

enables the electric "ow #which is

merely composed of electrons "owingacross a substance$ to travel through

the length of the metal.



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Semiconductors work in a verydi%erent manner. &ll intrinsicsemiconductors are group 14

elements, and thusly only have 'valence ( electrons available forbonding in their outermost shell.

)ecause of these ' electrons, group*' elements like Silicon are able to

form crystal lattice structures

composed of countless atoms of that



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Band Theory

!etals and semiconductors have aunique property that separates them

from non+conductive insulators. In

metals and insulators, the di%erencebetween energy orbitals are so small

that electrons can be ecited from lower

energy orbitals to higher energy levels.These small orbital energy di%erences

are referred to as bands.


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Band Theory

nlike the discrete energy levels thatyou are taught about in beginning

chemistry, these bands are so close

together in energy that it takes a verysmall amount of energy to promoteelectrons to these higher band levels.

The higher energy level that thevalence electrons can be ecited to isreferred to as the conduction band,

because the electrons in this band are

free to carry an electric current.


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Band Theory


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Hole Conduction

)y denition, an electron hole isthe opposite of an electron. It

represents the lack of an electronwhere an electron could potentially

be situated or previously wassituated in an otherwise full

electron shell. In this case,electron holes result from electrons

leaving their place in the lattice

structure .


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Hole Conduction

-nce heat is put into thesemiconductor and electrons begin

continually crossing into the

conduction band, hole conductionbegins constantly moving electronsacross the semiconductor, addingto the overall electron "ow. This

increases the conductive ability ofthe semiconductor, constantly

allowing new electrons to cross into

the conduction gap.


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Hole Conduction

lectron holes have an important rolein increasing the conductive abilitiesof semiconductors. /ole conduction

rst requires an electron toeperience ecitation in order to leave

its valence band to the conduction

band. -nce the valence electron hasleft, neighboring electrons are pulledinto the electron holes, lling eisting

electron holes while creating newneighboring ones.


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Intrinsic Semi Conductor Materials

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