Unlike metals, semiconductors increase their conductivity as you heat them (up to a point). Suggest an explanation.

Verified step by step guidance

Step 1: Understand the basic structure of semiconductors. Semiconductors have a band structure with a valence band filled with electrons and a conduction band that is empty at absolute zero temperature.

Step 2: Recognize the role of thermal energy. As temperature increases, thermal energy excites electrons from the valence band to the conduction band.

Step 3: Explain the increase in charge carriers. The excitation of electrons creates electron-hole pairs, increasing the number of charge carriers available for conduction.

Step 4: Discuss the effect on conductivity. With more charge carriers (electrons and holes), the electrical conductivity of the semiconductor increases.

Step 5: Note the limitations. This increase in conductivity continues up to a certain temperature, beyond which other effects, such as lattice vibrations, may dominate and affect conductivity differently.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Band Theory of Solids

Band theory explains the electronic structure of solids, distinguishing between conductors, insulators, and semiconductors. In semiconductors, the energy gap between the valence band and the conduction band is small, allowing electrons to jump into the conduction band when energy is supplied, such as through heat.

Temperature Dependence of Conductivity

In semiconductors, increasing temperature provides thermal energy that excites electrons from the valence band to the conduction band, enhancing conductivity. This contrasts with metals, where increased temperature causes increased lattice vibrations, impeding electron flow and reducing conductivity.

Intrinsic vs. Extrinsic Semiconductors

Intrinsic semiconductors are pure materials that conduct electricity due to thermally generated charge carriers, while extrinsic semiconductors have impurities added to enhance conductivity. The behavior of both types under temperature changes is crucial for understanding their conductivity variations with heat.

Recommended video:

Guided course

03:05

Ksp vs Q in Precipitation

Related Practice

Textbook Question

Silicon carbide, SiC, has the three-dimensional structure shown in the figure.

(b) Would you expect the bonding in SiC to be predominantly ionic, metallic, or covalent?

Textbook Question

Energy bands are considered continuous due to the large number of closely spaced energy levels. The range of energy levels in a crystal of copper is approximately 1 × 10^–19 J. Assuming equal spacing between levels, the spacing between energy levels may be approximated by dividing the range of energies by the number of atoms in the crystal. (b) Determine the average spacing in J between energy levels in the copper metal in part (a).

Textbook Question

Sodium oxide (Na2O) adopts a cubic structure with Na atoms represented by green spheres and O atoms by red spheres.