1. Semiconductor Physics.
Introduction to Semiconductors Information from Kittel’s book (Ch. 8) + many outside sources!!
Most lectures on semiconductors
will be based on those prepared for
Physics 5335
Semiconductor Physics.
That course was taught last in Fall,
2016. It is scheduled to be taught next
in the Fall of 2018!!

2. As discussed at the start of the semester, Phys. 5335, Semiconductor
Physics, has overlap with
this Solid State course.
But they are complementary
& are NOT the same.
I encourage you grad students to take Phys. 5335!
More information (last update, Dec., 2014!!) about Phys. 5335
is on the course webpages: 5335 Homepage:
5335 Lecture Page:

3. An Alternate Semiconductor Definition!

4. What is a Semiconductor? Kittel Ch. 8 & many other sources
Classification of Solids by their
Conductivity/Resistivity:
(σ = conductivity, ρ = resistivity)

5. What is a Semiconductor? Kittel Ch. 8 & many other sources
Classification of Solids by their
Conductivity/Resistivity:
(σ = conductivity, ρ = resistivity)
Metals: Good Conductors! :
103 ≤ σ ≤ 108 (Ω-cm)-1 ; ≤ ρ ≤ Ω-cm

6. What is a Semiconductor? Kittel Ch. 8 & many other sources
Classification of Solids by their
Conductivity/Resistivity:
(σ = conductivity, ρ = resistivity)
Metals: Good Conductors! :
103 ≤ σ ≤ 108 (Ω-cm)-1 ; ≤ ρ ≤ Ω-cm
Insulators: Poor Conductors!
σ ≤ 10-8 (Ω-cm)-1 ; ρ ≥ 108 Ω-cm

7. What is a Semiconductor? Kittel Ch. 8 & many other sources
Classification of Solids by their
Conductivity/Resistivity:
(σ = conductivity, ρ = resistivity)
Metals: Good Conductors! :
103 ≤ σ ≤ 108 (Ω-cm)-1 ; ≤ ρ ≤ Ω-cm
Insulators: Poor Conductors!
σ ≤ 10-8 (Ω-cm)-1 ; ρ ≥ 108 Ω-cm
Semiconductors/Semimetals:
10-8 ≤ σ ≤ 103 (Ω-cm)-1; ≤ ρ ≤ Ω-cm

8. What is a Semiconductor? Kittel Ch. 8 & many other sources
Classification of Solids by their
Conductivity/Resistivity:
(σ = conductivity, ρ = resistivity)
Metals: Good Conductors! :
103 ≤ σ ≤ 108 (Ω-cm)-1 ; ≤ ρ ≤ Ω-cm
Insulators: Poor Conductors!
σ ≤ 10-8 (Ω-cm)-1 ; ρ ≥ 108 Ω-cm
Semiconductors/Semimetals:
10-8 ≤ σ ≤ 103 (Ω-cm)-1; ≤ ρ ≤ Ω-cm
Note the HUGE range! Note also that there are no rigid boundaries!

9. Metals & Insulators: Measured resistivities range over more than 30 orders of magnitude!
Material
Resistivity (Ωm) (295K)
Resistivity (Ωm) (4K)
“Pure” Metals
Semi-
conductors
Ge (pure) 
Insulators
Potassium
Copper 
Diamond
P.T.F.E
(Polytetrafluoroethylene)

10. Metals, Insulators & Semiconductors
At low temperatures,
all materials are
insulators or metals.
1020-
Diamond
1010-
Resistivity (Ωm)
Germanium
Pure Metals:
Resistivity increases
rapidly with increasing
temperature.
100 -
Copper
10-10-
100
200
300
Temperature (K)
Semiconductors:
Resistivity decreases rapidly with increasing temperature.
Semiconductors have resistivities intermediate between
metals and insulators at room temperature.

11. Semiconductors Conductivity/Resistivity Definition
 Metals 
 Semimetals 

12. Semiconductors Conductivity/Resistivity Definition
Note the wide
range of
conductivity!
 Metals 
 Semimetals 

13. Conductivity/Resistivity of Some Materials
Semiconductors!

14. Conductivity of Some Materials

15. One Way to Classify “Electronic Materials”

16. Semiconductors: Bandgap Definition a semiconductor must also be
Semiconductors are ~ Small Bandgap Insulators
(we defined bandgap Eg earlier). Strictly speaking,
a semiconductor must also be
capable of being doped
(we’ll define doping later).

17. Semiconductors: Bandgap Definition a semiconductor must also be
Semiconductors are ~ Small Bandgap Insulators
(we defined bandgap Eg earlier). Strictly speaking,
a semiconductor must also be
capable of being doped
(we’ll define doping later).
Typical Bandgaps
Semiconductors: 0 ~ ≤ Eg ≤ ~ 3 eV

18. Semiconductors: Bandgap Definition a semiconductor must also be
Semiconductors are ~ Small Bandgap Insulators
(we defined bandgap Eg earlier). Strictly speaking,
a semiconductor must also be
capable of being doped
(we’ll define doping later).
Typical Bandgaps
Semiconductors: 0 ~ ≤ Eg ≤ ~ 3 eV
Metals & Semimetals: Eg = 0 eV

19. Semiconductors: Bandgap Definition a semiconductor must also be
Semiconductors are ~ Small Bandgap Insulators
(we defined bandgap Eg earlier). Strictly speaking,
a semiconductor must also be
capable of being doped
(we’ll define doping later).
Typical Bandgaps
Semiconductors: 0 ~ ≤ Eg ≤ ~ 3 eV
Metals & Semimetals: Eg = 0 eV
Insulators: Eg ≥ 3 eV

20. An Exception is Diamond
Eg = ~ 6 eV.
Diamond is usually considered an insulator, but it can be doped & used as a semiconductor!
Also, sometimes there is confusing terminology like:
GaAs: Eg = 1.5 eV
is sometimes called semi-insulating!

21. More Semiconductor Characteristics
In pure materials (very rare):
The electrical conductivity σ  exp(cT)
T = Kelvin Temperature, c = constant

22. More Semiconductor Characteristics
In pure materials (very rare):
The electrical conductivity σ  exp(cT)
T = Kelvin Temperature, c = constant
In Impure materials (most of them!):
The electrical conductivity σ depends strongly on impurity concentrations. “Doping” means to add impurities to change σ

23. More Semiconductor Characteristics
In pure materials (very rare):
The electrical conductivity σ  exp(cT)
T = Kelvin Temperature, c = constant
In Impure materials (most):
The electrical conductivity σ depends strongly on impurity concentrations. “Doping” means to add impurities to change σ
The electrical conductivity σ can be changed by light or electron radiation & by injection of electrons at contacts.

24. More Semiconductor Characteristics
In pure materials (very rare):
The electrical conductivity σ  exp(cT)
T = Kelvin Temperature, c = constant
In Impure materials (most):
The electrical conductivity σ depends strongly on impurity concentrations. “Doping” means to add impurities to change σ
The electrical conductivity σ can be changed by light or electron radiation & by injection of electrons at contacts
Transport of charge can occur by the motion of electrons or holes (defined later).

25. The Best Known Semiconductor is, of course, Silicon (Si)

26. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!

27. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!
Elemental: Si, Ge, C (diamond)

28. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!
Elemental: Si, Ge, C (diamond)
Binary Compounds: GaAs, InP, .

29. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!
Elemental: Si, Ge, C (diamond)
Binary Compounds: GaAs, InP, .
Organic Compounds: (CH)n (polyacetyline)

30. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!
Elemental: Si, Ge, C (diamond)
Binary Compounds: GaAs, InP, .
Organic Compounds: (CH)n (polyacetyline)
Magnetic Semiconductors: CdxMn1-xTe,…

31. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!
Elemental: Si, Ge, C (diamond)
Binary Compounds: GaAs, InP, .
Organic Compounds: (CH)n (polyacetyline)
Magnetic Semiconductors: CdxMn1-xTe,…
Ferroelectric Semiconductors: SbI, …

32. The Best Known Semiconductor is, of course, Silicon (Si)
However, there are
HUNDREDS (THOUSANDS?) of others!
Elemental: Si, Ge, C (diamond)
Binary Compounds: GaAs, InP, .
Organic Compounds: (CH)n (polyacetyline)
Magnetic Semiconductors: CdxMn1-xTe,…
Ferroelectric Semiconductors: SbI, …
Superconducting Compounds:
GeTe, SrTiO3, ..(“High Tc materials”)

33. Group IV Materials & III-V & II-VI Compounds
The Periodic Table: The Relevant Parts for Elemental & Binary Semiconductors
III IV V VI
II II
Group IV Materials & III-V & II-VI Compounds

34. Some Elements & Compounds which can be Semiconductors (Purple!)

35. Semiconductors (Main Constituents)

36. The Periodic Table Cloth!

37. Group IV Elements & III-V & II-VI Compounds

38. Group IV Elements & Compounds: Trends
Diamond
Diamond
Lattices
(α-Sn or gray tin)
The band gap (mostly) decreases & n-n distance
(mostly) increases going down a column or going
within a row from IV elements to III-V
compounds to II-VI compounds.

39. III-V & II-VI Compounds Trends
Zincblende or Wurtzite Lattices
The band gap (mostly) decreases &
n-n distance (mostly) increases
going down a column or going
within a row from IV elements to
III-V compounds to II-VI compounds.

40. Many Materials of Interest:
Have crystal lattice structures =
Diamond or Zincblende
(discussed in detail earlier!):
Each atom is tetrahedrally coordinated with four (4) nearest-neighbors.
The bonding is (mostly) sp3 hybrid bonding (strongly covalent).
Two atoms/unit cell (repeated to form an infinite solid).

41. Zincblende (ZnS) Lattice
Zincblende Lattice
The Cubic Unit Cell.
If all atoms are the
same, it becomes the
Diamond Lattice!
Zincblende Lattice
A Tetrahedral Bonding
Configuration

42. Zincblende/Diamond Lattices
Cubic Unit Cell
Zincblende Lattice
Cubic Unit Cell
Semiconductor Physicists & Engineers
need to know these structures!

43. Semiconductor Physicists & Engineers need to know these structures!
Diamond Lattice
Diamond Lattice
The Cubic Unit C`ell.
Semiconductor Physicists & Engineers
need to know these structures!

44. Zincblende (ZnS) Lattice
Zincblende Lattice
The Cubic Unit Cell.

45. Some Materials of Interest:
Have crystal lattice structures =
Wurtzite Structure
(discussed earlier!):
Similar to Zincblende, but has hexagonal symmetry instead of a cubic.
Each atom is tetrahedrally coordinated with four (4) nearest-neighbors.
The bonding is (mostly) sp3 hybrid bonding (strongly covalent).
Two atoms/unit cell (repeated to form an infinite solid).

46. Semiconductor Physicists & Engineers need to know these structures!
Wurtzite Lattice
Semiconductor Physicists & Engineers
need to know these structures!

47. Room Temperature Properties of Some Semiconductor Materials

48. Room Temperature Properties of
Some Semiconductors

49. Lattice Constants of Some Semiconductors

50. Room Temperature Properties of Si, Ge, & GaAs