Crystal Structure, Bonds, and Semiconductor Materials
From Atoms to Crystal Lattices
Covalent bonding and tetrahedral coordination
Group-IV semiconductors such as silicon and germanium form covalent bonds in a diamond cubic structure. Each atom shares four valence electrons with neighbors, creating a rigid periodic lattice that sets the allowed energy bands.
Why structure matters
The same element can behave very differently in different crystal forms because symmetry and bonding alter the band structure, effective masses, and defect sensitivity.
Common semiconductor families
Important materials include elemental semiconductors like and , compound semiconductors such as , , and , and emerging materials like and two-dimensional semiconductors such as . Each family trades off mobility, band gap, thermal robustness, and manufacturability.
Material property snapshot
| Material | Notable trait | Typical use |
|---|---|---|
| Silicon | Excellent manufacturing ecosystem | Logic and memory |
| Germanium | High mobility | Specialized high-speed devices |
| GaAs | High electron mobility | Microwave and optoelectronics |
| SiC | Wide band gap and high breakdown field | Power electronics |
| GaN | Very high breakdown strength | High-power RF and LEDs |
Which crystal structure is most closely associated with elemental silicon?
Silicon crystallizes in the diamond cubic structure, a tetrahedrally bonded lattice.
Correct answer: Diamond cubic
Name one reason silicon dominates microelectronics manufacturing.
Silicon combines adequate performance with low cost, abundant supply, and excellent oxide formation.
Correct answer: It has a mature manufacturing ecosystem
Why compound semiconductors are used
Compound semiconductors
- Can offer direct band gaps
- Often provide higher mobility or breakdown strength
Elemental semiconductors
- Usually cheaper and easier to process at scale
- Highly compatible with existing CMOS fabrication
Selecting a semiconductor material for an application
-
1
Define the target function, such as switching, amplification, or light emission.
-
2
Check the needed band gap, mobility, and thermal performance.
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3
Evaluate fabrication compatibility and cost.
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4
Choose the material family that best balances performance and manufacturability.
Which material is especially well suited to power electronics because of its wide band gap and high breakdown field?
Silicon carbide is widely used for high-voltage, high-temperature power devices.
Correct answer: SiC
What type of bonding primarily holds silicon atoms together in a crystal lattice?
Silicon atoms share valence electrons in strong covalent bonds.
Correct answer: Covalent bonding