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Jul 23
Semiconductors are materials that have an energy band structure that lies between that of conductors and insulators. In a semiconductor, there are two main energy bands - the valence band and the conduction band.
The valence band is the band of energy levels in which electrons are normally present in a solid material at absolute zero temperature. These electrons are tightly bound to the atoms in the material and do not have enough energy to move freely throughout the material.
The conduction band, on the other hand, is the band of energy levels above the valence band that electrons can move into when they are excited by an external energy source, such as heat or light. In a semiconductor, there is a small energy gap between the valence band and the conduction band, known as the band gap. This band gap is what distinguishes semiconductors from conductors and insulators.
When a semiconductor is exposed to energy, such as light or heat, some of the electrons in the valence band can be excited into the conduction band, creating electron-hole pairs. These electron-hole pairs can move freely throughout the material, allowing the semiconductor to conduct electricity. This property of semiconductors is what makes them essential for the functioning of electronic devices such as transistors, diodes, and integrated circuits.
The valence band is the band of energy levels in which electrons are normally present in a solid material at absolute zero temperature. These electrons are tightly bound to the atoms in the material and do not have enough energy to move freely throughout the material.
The conduction band, on the other hand, is the band of energy levels above the valence band that electrons can move into when they are excited by an external energy source, such as heat or light. In a semiconductor, there is a small energy gap between the valence band and the conduction band, known as the band gap. This band gap is what distinguishes semiconductors from conductors and insulators.
When a semiconductor is exposed to energy, such as light or heat, some of the electrons in the valence band can be excited into the conduction band, creating electron-hole pairs. These electron-hole pairs can move freely throughout the material, allowing the semiconductor to conduct electricity. This property of semiconductors is what makes them essential for the functioning of electronic devices such as transistors, diodes, and integrated circuits.
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Google Gemini AI
Jul 23
Semiconductors in Terms of Energy Bands
In a semiconductor, the valence band (VB) and the conduction band (CB) are separated by an energy gap, known as the bandgap.
Valence Band (VB)
- The valence band is the highest energy band that is occupied by electrons at absolute zero temperature.
- In semiconductors, the valence band is typically filled with valence electrons that are tightly bound to their atomic nuclei.
Conduction Band (CB)
- The conduction band is the lowest energy band that is unoccupied by electrons at absolute zero temperature.
- In semiconductors, the conduction band is typically empty at low temperatures.
Bandgap
- The bandgap (Eg) is the energy difference between the top of the valence band and the bottom of the conduction band.
- For semiconductors, the bandgap is typically in the range of 0.1 to 4 eV.
Intrinsic Semiconductors
- In intrinsic semiconductors, the bandgap is large enough to prevent electrons from naturally jumping from the valence band to the conduction band at room temperature.
- As a result, intrinsic semiconductors have very low electrical conductivity.
Extrinsic Semiconductors
- Extrinsic semiconductors are created by adding impurities (dopants) to the semiconductor material.
- Dopants can either decrease the bandgap (n-type doping) or increase the bandgap (p-type doping).
N-Type Semiconductors
- In n-type semiconductors, dopants with more valence electrons than the semiconductor atoms are added (e.g., phosphorus).
- These extra valence electrons create donor energy levels just below the conduction band.
- Electrons from these donor levels can easily move into the conduction band, making n-type semiconductors more conductive.
P-Type Semiconductors
- In p-type semiconductors, dopants with fewer valence electrons than the semiconductor atoms are added (e.g., boron).
- These missing valence electrons create acceptor energy levels just above the valence band.
- Holes (vacant electron positions) can easily move into these acceptor levels, making p-type semiconductors more conductive.
Conduction in Semiconductors
- In semiconductors, conduction occurs when electrons move from the valence band to the conduction band.
- This can occur through thermal excitation, doping, or the application of an electric field.
- The electrical conductivity of semiconductors is strongly influenced by the bandgap, dopant concentration, and temperature.
In a semiconductor, the valence band (VB) and the conduction band (CB) are separated by an energy gap, known as the bandgap.
Valence Band (VB)
- The valence band is the highest energy band that is occupied by electrons at absolute zero temperature.
- In semiconductors, the valence band is typically filled with valence electrons that are tightly bound to their atomic nuclei.
Conduction Band (CB)
- The conduction band is the lowest energy band that is unoccupied by electrons at absolute zero temperature.
- In semiconductors, the conduction band is typically empty at low temperatures.
Bandgap
- The bandgap (Eg) is the energy difference between the top of the valence band and the bottom of the conduction band.
- For semiconductors, the bandgap is typically in the range of 0.1 to 4 eV.
Intrinsic Semiconductors
- In intrinsic semiconductors, the bandgap is large enough to prevent electrons from naturally jumping from the valence band to the conduction band at room temperature.
- As a result, intrinsic semiconductors have very low electrical conductivity.
Extrinsic Semiconductors
- Extrinsic semiconductors are created by adding impurities (dopants) to the semiconductor material.
- Dopants can either decrease the bandgap (n-type doping) or increase the bandgap (p-type doping).
N-Type Semiconductors
- In n-type semiconductors, dopants with more valence electrons than the semiconductor atoms are added (e.g., phosphorus).
- These extra valence electrons create donor energy levels just below the conduction band.
- Electrons from these donor levels can easily move into the conduction band, making n-type semiconductors more conductive.
P-Type Semiconductors
- In p-type semiconductors, dopants with fewer valence electrons than the semiconductor atoms are added (e.g., boron).
- These missing valence electrons create acceptor energy levels just above the valence band.
- Holes (vacant electron positions) can easily move into these acceptor levels, making p-type semiconductors more conductive.
Conduction in Semiconductors
- In semiconductors, conduction occurs when electrons move from the valence band to the conduction band.
- This can occur through thermal excitation, doping, or the application of an electric field.
- The electrical conductivity of semiconductors is strongly influenced by the bandgap, dopant concentration, and temperature.
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