Figure 16.31: Two-dimensional representations of
(a) a quartz crystal and (b) a quartz glass.
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16a–1
Figure 16.28: The p orbitals (a) perpendicular to the plane of
th carbon ring system in graphite can combine to form
(b) an extensive pie bonding network.
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16a–2
The Electronic Configuration of a Magnesium Atom
n
3
3
l
0
0
ml ms
0 +1/2
0 -1/2
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Empty 3p
orbitals in Mg
valence shell
3p
Mg: (Ne)3s2
3s
2p
2s
1s
16a–3
Orbital energy
levels
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16a–4
Figure 16.24: A representation of the energy
levels (bands) in a magnesium crystal
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16a–5
Figure 16.27: Partial representation of the MO
energies in (a) diamond and (b) a typical metal
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16a–6
Electron sea model for
metals
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16a–7
Bonding in Solids
Metallic Solids
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16a–8
Band structure of Semiconductors
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16a–9
Band Diagram: Semiconductor with No Doping
T>0
Conduction band
(Partially Filled)
EC
EF
EV
Valence band
(Partially Empty)
• At T = 0, lower valence band is filled with electrons and upper
conduction band is empty, leading to zero conductivity.
– Fermi energy EF is at midpoint of small energy gap (<1 eV)
between conduction and valence bands.
• At T > 0, electrons thermally “excited” from valence to conduction
band, leading to measurable conductivity.
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16a–10
Silicon Crystal
Doped with (a)
Arsenic and (b)
Boron
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16a–11
Figure 16.33: Energy-level diagrams for (a) an
n-type semiconductor and (b) a p-type semiconductor.
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16a–12
pn junction
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16a–13
Figure 16.34: The p-n junction involves the
contact of a p-type and an n-type semiconductor.
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16a–14
PN Junction - 7
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16a–15
PN Junction with Applied Potential
No current, Barrier Larger
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Current Flows, Barrier Smaller
16a–16
Herbert Kroemer
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16a–17
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16a–18
Light Amplification by Stimulated Emission Radiation
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16a–19
Solar Cells
Electron
p-type
n-type
Hole
Photons
Load
p-n Junction under Illumination
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16a–20
Solar Panels – Photovoltaic Cells
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16a–21
Schematic of a Photovoltaic (solar) cell
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16a–22
A schematic of two circuits
connected by a transistor.
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16a–23
Photolithography to make semiconductor
integrated circuits
http://britneyspears.ac/physics/fabrication/photolithography.htm
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16a–24
(a)-(h) The steps for forming a transistor in a
crystal of initially pure silicon.
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16a–25
(a)-(h) The steps for forming a transistor in a
crystal of initially pure silicon. (cont’d)
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16a–26
Semiconductors – key points to remember
• Band structure:
Valence band – gap – conduction band
•DOPING:
Group V  n type,
Group III  p type
•n-p junctions
•Devices:
(LED, laser, transistor, solar cell)
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16a–27
Figure 16.24: A representation of the energy
levels (bands) in a magnesium crystal
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16a–28
Band structure of Semiconductors
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16a–29
Semiconductors – key points to remember
• Band structure:
Valence band – gap – conduction band
•DOPING:
Group V  n type,
Group III  p type
•n-p junctions
•Devices:
(LED, laser, transistor, solar cell)
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16a–30
Silicon Crystal
Doped with (a)
Arsenic and (b)
Boron
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16a–31
Semiconductors – key points to remember
• Band structure:
Valence band – gap – conduction band
•DOPING:
Group V  n type,
Group III  p type
•n-p junctions
•Devices:
(LED, laser, transistor, solar cell)
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16a–32
pn junction
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16a–33
Semiconductors – key points to remember
• Band structure:
Valence band – gap – conduction band
•DOPING:
Group V  n type,
Group III  p type
•n-p junctions
•Devices:
(LED, laser, transistor, solar cell)
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16a–34
C60 crystals
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16a–35
Ionic liquids
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16a–36