Conduction of Electricity in Semiconductors – Class 12 | Chapter – 1 | Chemistry Short Notes Series PDF for NEET & JEE
Conduction of Electricity in Semiconductors: Semiconductors are materials that have electrical conductivity between that of metals and insulators. The conduction of electricity in semiconductors is different from that in metals and is primarily due to the behavior of electrons in the valence and conduction bands of the material. In a semiconductor, the valence band is the highest energy level occupied by electrons, while the conduction band is the lowest energy level that is unoccupied. When an electric field is applied to a semiconductor, electrons in the valence band can be excited to the conduction band, creating a flow of current through the material.
Properties of Conduction of Electricity in Semiconductors
Semiconductors are materials that have electrical conductivity between that of conductors (e.g., metals) and insulators (e.g., ceramics). The conduction of electricity in semiconductors is governed by several important properties, including:
- Band structure: Semiconductors have a specific band structure where the valence band is occupied by electrons, and the conduction band is empty. The energy gap between the valence and conduction bands, called the bandgap, is relatively small, allowing electrons to jump from the valence band to the conduction band when excited.
- Doping: Semiconductors can be doped with impurities to alter their electrical properties. N-type doping involves adding impurities that donate electrons to the semiconductor, creating excess electrons in the conduction band. P-type doping involves adding impurities that accept electrons from the semiconductor, creating holes in the valence band.
- Temperature: The conductivity of semiconductors increases with temperature due to increased thermal energy, which allows more electrons to jump from the valence band to the conduction band.
- Mobility: The mobility of electrons and holes in semiconductors determines how easily they move through the material. Mobility is affected by factors such as impurity concentration, crystal structure, and temperature.
- Electron-hole recombination: When electrons and holes meet, they can recombine, releasing energy in the form of light or heat. This process is important in semiconductor devices such as LEDs and solar cells.
- Electric field: The conduction of electricity in semiconductors can be influenced by an applied electric field, which can either enhance or hinder the flow of electrons and holes through the material.
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