Band Theory of Semiconductors

Introduction

• The band theory of semiconductors explains the electrical properties of semiconductor materials, which lie between conductors and insulators.
• Semiconductors have unique band structures that allow them to exhibit variable conductivity.

Semiconductor Band Structure

• Unlike insulators with large band gaps and conductors with overlapping bands, semiconductors have a moderate band gap between the valence and conduction bands.
• At room temperature, some electrons have enough thermal energy to transition from the valence band to the conduction band.

Room Temperature Conductivity

• At room temperature, semiconductors have sufficient thermal energy to enable electron movement into the conduction band.
• This electron transition creates charge carriers (free electrons) in the conduction band, allowing for some electrical conduction.
• The presence of charge carriers makes semiconductors conductive, though less so than metals (conductors).

Temperature Influence

• Increasing the temperature of a semiconductor enhances its conductivity.
• Higher temperatures provide more thermal energy to electrons, allowing a greater number of them to transition into the conduction band.
• This increased availability of charge carriers results in improved electrical conduction

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Band Theory of Semiconductors

Key Points

• Semiconductors have a moderate band gap between the valence and conduction bands.
• At room temperature, some electrons have enough thermal energy to move into the conduction band, allowing for limited conductivity.
• Increasing temperature enhances semiconductor conductivity.
• Doping, through the introduction of impurities, can significantly modify a semiconductor's band structure and electrical properties.

Summary

• The band theory of semiconductors explains how these materials, with their moderate band gap, exhibit variable conductivity based on temperature and doping.
• By controlling the band structure through temperature and intentional doping, semiconductors can be tailored for various electronic applications.