At very high temperatures the extrinsic semi conductors become intrins...
At very high temperatures, the extrinsic semiconductors become intrinsic due to the dominance of band-to-band transitions over impurity ionization. This transition occurs because of the increased thermal energy that allows electron-hole pairs to be generated without the influence of impurities.
Explanation:
- High temperatures provide sufficient thermal energy to excite electrons from the valence band to the conduction band, creating electron-hole pairs.
- In extrinsic semiconductors, impurity ions (dopants) are added intentionally to control the conductivity. These dopants introduce additional energy levels within the band gap, either above or below the intrinsic energy levels.
- At lower temperatures, the majority of the electrons and holes are generated by the ionization of the dopants. This means that impurity ionization dominates the generation of charge carriers, and the semiconductor remains extrinsic.
- However, at very high temperatures, the thermal energy is sufficient to excite electrons from the valence band to the conduction band directly, without the need for ionization of impurity dopants.
- This band-to-band transition dominates the generation of electron-hole pairs, and the semiconductor behaves more like an intrinsic semiconductor.
- Intrinsic semiconductors are pure semiconducting materials without any intentional impurities. They have their own energy levels within the band gap due to the crystal lattice structure.
- When extrinsic semiconductors become intrinsic at high temperatures, it means that the majority of the charge carriers are generated through band-to-band transitions, rather than the ionization of impurities.
- This transition is significant because it affects the electrical conductivity and other properties of the semiconductor material.
- It is important to note that this transition is only valid for very high temperatures, as at lower temperatures, the influence of impurities becomes dominant again.
In summary, at very high temperatures, extrinsic semiconductors become intrinsic due to the dominance of band-to-band transitions over impurity ionization. The increased thermal energy allows for the direct generation of electron-hole pairs without the need for dopant ionization.
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