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semiconductor � What it is?
� Conductors and insulators
� Semiconductor
� Band occupation and conductivity
� The Conductivity Gap
� Semiconductor Theory
� Devices
PHYS3305 Jasmine Liu 2
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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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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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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