Semiconductor - SMU Physics...semiconductor ! What it is? ! Conductors and insulators !...

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Semiconductor PHYS3305 Jasmine Liu PHYS3305 Jasmine Liu 1

Transcript of Semiconductor - SMU Physics...semiconductor ! What it is? ! Conductors and insulators !...

Semiconductor PHYS3305 Jasmine Liu

PHYS3305 Jasmine Liu 1

semiconductor �  What it is?

�  Conductors and insulators

�  Semiconductor

�  Band occupation and conductivity

�  The Conductivity Gap

�  Semiconductor Theory

�  Devices

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What is semiconductor? First, what are insulators and conductors?

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Band Occupation and Conductivity �  Bands

�  Conductor: lithium

�  Insulator: beryllium ? �  Overlapped 2s and 2p �  Changeable bands

�  Valance band

�  Conduction band

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Semiconductor �  T= 0, insulator

�  Small gap between the valence and conduction bands

�  Smaller than 2eV

�  Elements: silicon and germanium (lesser)

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The Conductivity Gap �  Relationship between temperature and conductivity

�  Fermi-Dirac distribution

�  The number of electrons <= 1

�  Fermi energy falls between the

valance and conduction bands

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Semiconductor Theory �  Electronic switching (e.g. diode)

�  Positive charge carriers: holes

�  Doping �  p-n type

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Holes

�  Hall effect

�  Thermal excitation

�  Holes float

�  Effective mass

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Doping �  Extrinsic semiconductors

�  n-type �  donor state

�  p-type �  acceptor states

�  Minority carriers and majority carriers

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Application �  Diode

�  a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.

�  Transistor �  a semiconductor device used to amplify and switch

electronic signals and electrical power.

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Diode �  p-n junction

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Transistor �  Invention in 1947,by John Bardeen

�  Evolution from resistors, capacitors, diodes, and inductors

�  Adjust the flow of electricity in variable amounts

�  npn type

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Conclusion semiconductor

�  Applied to materials that are insulators at zero temperature

�  The gap between the valence and conduction bands is small (<= 2eV)

�  Silicon and germanium used in electronic devices

�  Examples: transistor and diode

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References �  Harris, Randy, and Randy Harris. Modern Physics.

Second ed. San Francisco: Pearson/Addison Wesley, 2008.

�  Sze, S. M. Physics of Semiconductor Devices. 2nd ed. New York: Wiley, 1981.

�  The Essential Guide to Semiconductors. 27 Vol. Portland: Ringgold Inc, 2003.

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