lecture_3_chex42

lecture_3_chex42 - Semiconductors Semiconductors Materials...

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Semiconductors Semiconductors • Materials that are neither metallic nor insulator. • Elemental Semiconductors: Si, Ge • Si dominates IC industry: >99% is Si based devices) • Compound Semiconductors – III-V semiconductors : GaAs (most widely used compound semiconductor), InSb, InP – II-VI semiconductors: CdS, ZnSe, ZnO • Alloy Semiconductors: HgCdTe, Al x Ga 1-x , As, GaAs x P 1-x
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Semiconductors Semiconductors
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Semiconductor Models Semiconductor Models Bonding Model Bonding Model ¾ Lines represent shared valence electron ¾ Circle represent the core of Semiconductor (e.g., Si atom) ¾ Visualization of a vacancy point defect ¾ Breaking of an atom- to-atom bond and freeing of an electron http://www.play-hookey.com/semiconductors/basicstructure.html
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Review: Molecular Review: Molecular Orbitals Orbitals by linear combination of atomic by linear combination of atomic orbitals orbitals Ψ = Ψ E H Quantum mechanics www.chembio.uoguelph.ca/educmat/ chm729/band/basic2.jpg
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Semiconductor Models Semiconductor Models Energy Band Model Energy Band Model ¾ Energy states bunch up into “bands” and energy states are so close to each other in energy that they are approximately continuous. ¾ Depending on the energy difference between the bonding and antobonding orbitals a gap opens up between the bands corresponding to the bonding and antibonding orbitals where there are no allowed energy levels www.chembio.uoguelph.ca/educmat/ chm729/band/basic2.jpg
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Energy Band Model Energy Band Model
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Band gaps of common semiconductors Band gaps of common semiconductors
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The difference between insulators, semiconductors, The difference between insulators, semiconductors, and metals in the band theory framework and metals in the band theory framework Gap is very wide ~ 8 eV for SiO 2 ~ 5 eV for diamond thermal excitation is easy kT~0.026 eV ~ 1.12 eV for Si No or very narrow gap Few electrons Thermal excitation of electrons is easy kT 2 E g e ~
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This note was uploaded on 12/29/2011 for the course CHE 142 taught by Professor Ceweb during the Fall '09 term at UCSB.

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lecture_3_chex42 - Semiconductors Semiconductors Materials...

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