Difference between revisions of "Semiconductors"

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==Conductors and Insulators==
Conductors are able to accomodate an electron flow through them because the electrons in the atoms are not tightly bound to thier atoms. When an electron leaves its atom, it leaves behind '''hole''', which because of the absence of the electron, is positivly charged since the atom started out neutral. This hole can be modeled as a positive charge. As electrons move towards one end of the conductor, they will leave holes at the opposite end, thus creating a "flow" of holes in the direction opposite the electron flow.
Conductors are able to accomodate an electron flow through them because the electrons in the atoms are not tightly bound to thier atoms. When an electron leaves its atom, it leaves behind '''hole''', which because of the absence of the electron, is positivly charged since the atom started out neutral. This hole can be modeled as a positive charge. As electrons move towards one end of the conductor, they will leave holes at the opposite end, thus creating a "flow" of holes in the direction opposite the electron flow.


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[[Image:insulator_diagram.jpg]]
[[Image:insulator_diagram.jpg]]


==Semiconductors==
Semiconductors allow us to build ''non-linear'' devices, such as computers.
Semiconductors, such as silicon, are somewhere in between a conductor and an insulator. Some electrons in the semi-conducor are allowed to flow, especially when relased by heat or light. Semiconductors allow us to build ''non-linear'' devices, such as computers.

We can increase the conductivity of semiconductors by ''doping'', or interspersing atoms with more valence electrons into the lattice structure.

For example, we can dope silicon (which as four valence electrons) with arsenic (which has 5 valence electrons). The extra electron in the arsenic atom cannot form a covalent bond with the neighboring atoms, and thus is loosely bound and available as a charge carrier. This creates an '''n-type'' semiconductor, which has negative charge carriers.

We can also dope the silicon with boron or galium, which have 3 valence electrons. The lack of an electron to complete all four covalent bonds the lattice structure leaves a hole into which an electron can fall. This creates a '''p-type''' semiconductor, which has positive charge charriers.

Revision as of 15:35, 16 June 2006

Conductors and Insulators

Conductors are able to accomodate an electron flow through them because the electrons in the atoms are not tightly bound to thier atoms. When an electron leaves its atom, it leaves behind hole, which because of the absence of the electron, is positivly charged since the atom started out neutral. This hole can be modeled as a positive charge. As electrons move towards one end of the conductor, they will leave holes at the opposite end, thus creating a "flow" of holes in the direction opposite the electron flow.

File:Conductor diagram.jpg

The electrons in insulators are tightly bound to thier atoms, so they cannot flow.

File:Insulator diagram.jpg

Semiconductors

Semiconductors, such as silicon, are somewhere in between a conductor and an insulator. Some electrons in the semi-conducor are allowed to flow, especially when relased by heat or light. Semiconductors allow us to build non-linear devices, such as computers.

We can increase the conductivity of semiconductors by doping, or interspersing atoms with more valence electrons into the lattice structure.

For example, we can dope silicon (which as four valence electrons) with arsenic (which has 5 valence electrons). The extra electron in the arsenic atom cannot form a covalent bond with the neighboring atoms, and thus is loosely bound and available as a charge carrier. This creates an 'n-type semiconductor, which has negative charge carriers.

We can also dope the silicon with boron or galium, which have 3 valence electrons. The lack of an electron to complete all four covalent bonds the lattice structure leaves a hole into which an electron can fall. This creates a p-type semiconductor, which has positive charge charriers.