Solid-state physics: conduction Prof. Stephen Sekula (3/30/2010) Supplementary Material for PHY 3305 (Modern Physics) Harris, Ch. 10.6-10.8
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Solid-state physics: conduction
Prof. Stephen Sekula(3/30/2010)
Supplementary Material for PHY 3305 (Modern Physics)
Harris, Ch. 10.6-10.8
table of contents
● Review
● Bands (T=0, T>0)
● Lithium vs. Beryllium
● Band Pictures
● Holes
● Semiconductors● intrinsic and extrinsic
● Example: Diode
● Example: Transistor
solid, no Electric field applied
Equal populations of -k and +k electrons
solid, WITH Electric field applied
A picture: bands/Gaps
N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Gap
A picture: bands/Gaps
N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Gap
Energy levels so close as to resemble a continuum
Energy levels so close as to resemble a continuum
Questions
● How many conduction electrons can each band hold?
● Which is a better conductor: Lithium or Beryllium?● Lithium has 3 electrons● Beryllium has 4 electrons
Insulator (T=0)N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Empty(Conduction Band)
Full(Valence Band)
conductor (T=0)N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Partially Full
Full
Semi-Conductor (T=0)N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Empty
Full
conductor (T>0)N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Partially Full
Full
Semi-Conductor (T>0)N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Mostly Empty
Mostly Full
HOLES (T>0)N s
tate
s pe
r ba
n dN s
tate
s pe
r ba
n d
Conduction Band
Valence Band
Temperature causes an
electron to jump the gap, leaving a
“hole” in the valence band.
Holes floatN s
tate
s pe
r ba
n d
Valence Band
Total Energy E1
N s
tate
s pe
r ba
n d
Valence Band
Total Energy E2
E2 < E1
n-type extrinsic semiconductor (T=0)
N s
tate
s pe
r ba
n d
Conduction Band
Valence Band
Donor States
0.05 eV
N s
tate
s pe
r ba
n d
n-type extrinsic semiconductor (T>0)
N s
tate
s pe
r ba
n d
Conduction Band
Valence Band
N s
tate
s pe
r ba
n d
Donor States
0.05 eV
N s
tate
s pe
r ba
n d
P-type extrinsic semiconductor (T=0)
N s
tate
s pe
r ba
n d
Conduction Band
Valence Band
Acceptor States 0.05 eV
N s
tate
s pe
r ba
n d
P-type extrinsic semiconductor (T>0)
N s
tate
s pe
r ba
n d
Conduction Band
Valence Band
N s
tate
s pe
r ba
n d
Acceptor States 0.05 eV
N s
tate
s pe
r ba
n d
the diode
energy band picture
Transistor
Next time
● Superconductivity● Nuclear Physics● Good presentation style● Reading for next time: Harris Ch. 10.9, 11.1-11.2
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