Embed Size (px)
Citation preview
Lundstrom ECE-305 S16
ECE-305: Spring 2016
Material Properties: I
Professor Mark Lundstrom Electrical and Computer Engineering
Purdue University, West Lafayette, IN USA [email protected]
1/12/15
Pierret, Semiconductor Device Fundamentals (SDF) pp. 3-11
1
semiconductors
“One shouldn’t work on semiconductors, that is a filthy mess; who knows whether any semiconductors exist.” Wolfgang Pauli, 1931
Lundstrom ECE-305 S16 2
Lundstrom ECE-305 S16 3
outline
1. Silicon
2. Crystals
semiconductors
4
http://en.wikipedia.org/wiki/Periodic_table
column IV
Lundstrom ECE-305 S16
5
silicon energy levels
1S2
2S2
2P6
3S2
3P2
4S0
Si atom (At. no. 14)
4 valence electrons 8 valence states
“core levels”
Lundstrom ECE-305 S16
ener
gy
Si atoms in a solid
6
1) In a Si crystal, each atom occupies, a specific location in a crystal lattice.
2) Polycrystalline Si consider of many
crystalline “grains” with different orientations. 3) In amorphous Si, the atoms are more or less
randomly distributed throughout the solid.
Lundstrom ECE-305 S16
a 2D crystal
7 Lundstrom ECE-305 S16
a
b
Graphene: 2011 Nobel Prize in Physics
8
Graphene is a one-atom-thick planar carbon sheet with a honeycomb lattice.
source: CNTBands 2.0 on nanoHUB.org
Lundstrom ECE-305 S16
unit cells
9 Lundstrom ECE-305 S16
3D crystal structure
10 Lundstrom ECE-305 S16 http://en.wikipedia.org/wiki/Bravais_lattice
lattice plus basis
11 Lundstrom ECE-305 S16
semiconductors
12
http://en.wikipedia.org/wiki/Periodic_table
column IV
semiconductors
13
http://en.wikipedia.org/wiki/Periodic_table
Col. III
Col. V
14
Si crystal structure (diamond lattice)
Natoms ≈ 5×1022 cm-3
5.43 A
Lundstrom ECE-305 S16
4 nearest neighbors
Lundstrom ECE-305 S16 15
diamond lattice
https://nanohub.org/tools/crystal_viewer
Lundstrom ECE-305 S16 16
The diamond lattice
https://nanohub.org/tools/crystal_viewer
Atoms per unit cell 8 times 1/8 + 6 times ½ + 4 8 atoms per unit cell
Lundstrom ECE-305 S16 17
Silicon: density
https://nanohub.org/tools/crystal_viewer
Lattice constant: a = 5.4307 Ang Density = total mass/vol. of unit cell. Atomic mass of Si: 28.0855 amu 1 amu = 1.6605 x 10−27 kg
ρ = 8× 28.0855×1.6605×10−27
5.4307 ×10−10( )3 kg/m3
ρ = 2.3296 g/cm3
Lundstrom ECE-305 S16 18
Silicon: NN spacing
https://nanohub.org/tools/crystal_viewer
Lattice constant: a = 5.4307 Ang Body diagonal = sqrt(3) a. NN spacing = sqrt(3)a/4
“cartoon” Si crystal
Lundstrom ECE-305 S16 19
Lundstrom ECE-305 S16 20
outline
1. Silicon
2. Crystals
✔
✔
https://nanohub.org/tools/crystal_viewer Online tool:
