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Questions and Answers
What creates an electron-hole pair in a silicon crystal?
What creates an electron-hole pair in a silicon crystal?
In an intrinsic silicon crystal at absolute 0 Kelvin, there are conduction electrons present.
In an intrinsic silicon crystal at absolute 0 Kelvin, there are conduction electrons present.
False
What happens to an electron when it moves from the valence band to the conduction band?
What happens to an electron when it moves from the valence band to the conduction band?
It becomes a free electron.
Electrons that have energy and are free to move within a semiconductor are called __________.
Electrons that have energy and are free to move within a semiconductor are called __________.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What is the net charge of the core of a silicon atom?
What is the net charge of the core of a silicon atom?
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The valence electron in copper is held with more force than in silicon.
The valence electron in copper is held with more force than in silicon.
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What characteristic do both silicon and germanium share?
What characteristic do both silicon and germanium share?
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The valence electrons in germanium are in the ______ shell, which is at a higher energy level compared to silicon.
The valence electrons in germanium are in the ______ shell, which is at a higher energy level compared to silicon.
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Match the following elements with their characteristic amounts of valence electrons:
Match the following elements with their characteristic amounts of valence electrons:
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Study Notes
Semiconductor vs. Conductor Atoms
- Semiconductor atoms (like silicon) have a net positive core charge (+4) and valence electrons in the third shell.
- Conductor atoms (like copper) have a net positive core charge (+1) and valence electrons in the fourth shell.
- Valence electrons in conductors are further out from the nucleus, thus requiring less energy to become free electrons. This is why they are conductors.
- Valence electrons in semiconductors are closer to the nucleus, requiring more energy to become free electrons. This is why they are semiconductors.
Covalent Bonds in Silicon and Germanium
- Silicon and germanium atoms both have four valence electrons.
- These atoms share an electron with each of their four neighbors to form eight shared valence electrons.
- This creates a stable structure via covalent bonds.
- Silicon is a more commonly used semiconductor material due to its less instability at high temperatures.
Energy Band Diagram for Silicon
- Electrons in a solid can only exist within discrete energy levels called "bands".
- There are bands for valence electrons and conduction electrons.
- A band gap separates these bands. No electrons can exist in the band gap.
- In pure silicon at 0 Kelvin (absolute zero), there are no electrons in the conduction band.
- At higher temperatures, heat energy can promote valence electrons to the conduction band.
Electron-Hole Pairs
- Electrons that jump the band gap into the conduction band leave behind "holes" in the valence band.
- This creates an electron-hole pair that contributes to electrical conduction.
- Recombination occurs when electrons fall back into holes. This process is continuing at a given temperature.
Conduction Current (Electron Current)
- Conduction current involves electrons moving through the conduction band to the positive electrode.
- The movement of electrons is the conduction current.
Hole Current
- Hole current involves electrons moving within the valence band to fill holes, creating the appearance of "positive" charge movement.
- The "movement" of holes is actually the movement of negatively charged electrons filling valence band holes.
Conduction in Semiconductors
- Conduction in semiconductors is due to either the movement of free electrons or the movement of holes.
- These movements are opposing in direction.
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Description
Test your knowledge on the differences between semiconductor and conductor atoms, focusing on their atomic structure and bonding. This quiz also covers the covalent bonds in silicon and germanium, along with the energy band diagram concepts. Answer questions to reinforce your understanding of these important materials.
