Conductivity

Definition

Conductivity is the ability of a material to conduct electric current, which is determined by the presence and mobility of charge carriers, such as electrons or holes. In metals, conductivity arises from free electrons that can move easily through the lattice structure, while in semiconductors, conductivity can change significantly with temperature and impurity levels. Understanding conductivity is essential for analyzing the electronic properties of various materials, including metals and semiconductors.

5 Must Know Facts For Your Next Test

1. In the free electron model, high conductivity in metals is attributed to the large number of delocalized electrons that can move freely throughout the material.
2. Intrinsic semiconductors have a relatively low conductivity at absolute zero but experience increased conductivity as temperature rises due to thermal excitation of electrons.
3. Extrinsic semiconductors have their conductivity enhanced by doping with impurities, which introduces additional charge carriers, increasing the overall conductivity.
4. The nearly free electron model accounts for the weak periodic potential in a crystal lattice that allows for some interaction between conduction electrons and the lattice, affecting conductivity.
5. Temperature dependence plays a crucial role in the conductivity of both intrinsic and extrinsic semiconductors, with conductivity typically increasing with temperature due to increased charge carrier mobility.

Review Questions

• How does the free electron model explain high conductivity in metals compared to semiconductors?
  • The free electron model explains high conductivity in metals by considering that metals have a large number of free electrons that can move freely throughout the lattice structure. These delocalized electrons are not bound to any specific atom and can easily respond to an electric field, leading to high current flow. In contrast, semiconductors lack such a high density of free electrons at low temperatures, resulting in much lower conductivity until thermal energy or doping increases the number of available charge carriers.
• What role does doping play in enhancing the conductivity of extrinsic semiconductors?
  • Doping introduces impurity atoms into an intrinsic semiconductor, creating additional charge carriers—either electrons or holes—depending on whether it is n-type or p-type doping. This increases the number of charge carriers available for conduction, significantly boosting the overall conductivity of the semiconductor. Doping essentially tailors the electrical properties of semiconductors for various applications in electronic devices.
• Evaluate how temperature variations affect the conductivity of intrinsic and extrinsic semiconductors and explain the underlying mechanisms involved.
  • Temperature variations greatly influence the conductivity of both intrinsic and extrinsic semiconductors due to their dependence on charge carrier dynamics. In intrinsic semiconductors, increasing temperature provides sufficient energy to excite electrons from the valence band to the conduction band, thereby increasing conductivity. Conversely, in extrinsic semiconductors, temperature changes can also affect carrier mobility; while higher temperatures may enhance carrier generation, they can also scatter carriers more effectively, complicating their overall impact on conductivity. The interplay between thermal excitation and scattering events creates a unique behavior pattern in response to temperature changes.

Related terms

Resistivity: Resistivity is a measure of a material's opposition to the flow of electric current, inversely related to conductivity. It indicates how strongly a material resists current flow.

Charge Carrier: Charge carriers are particles, such as electrons or holes, that carry electric charge through a material. Their density and mobility significantly affect the conductivity of a substance.

Band Gap:

The band gap is the energy difference between the valence band and conduction band in semiconductors. It determines how easily electrons can be excited to contribute to conductivity.