Definition of bandgap

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Photonics Dictionary

bandgap: In semiconductor physics, the term bandgap refers to the energy range in a material where no electronic states are allowed. It represents the energy difference between the valence band, which is the highest range of energy levels occupied by electrons in their ground state, and the conduction band, which is the lowest range of unoccupied energy levels. The bandgap is a crucial parameter in understanding the electrical behavior of semiconductors and insulators.

Here are the key components related to the bandgap:

Valence band: The valence band is the highest energy band in which electrons reside at absolute zero temperature. Electrons in the valence band are typically involved in bonding between atoms.

Conduction band: The conduction band is the next higher energy band that electrons can access. Electrons in the conduction band have sufficient energy to move freely and contribute to electrical conduction.

Bandgap energy: The bandgap energy is the energy difference between the top of the valence band and the bottom of the conduction band. It is typically measured in electron volts (eV) or joules. A larger bandgap means that the material is more insulating, as it requires a higher energy input for electrons to move from the valence band to the conduction band.

Electron excitation: Electrons can be excited from the valence band to the conduction band by gaining energy, typically through the absorption of photons (light). This process is essential for the operation of semiconductor devices like solar cells and LEDs.

Semiconductor classification: Materials are often classified as conductors, semiconductors, or insulators based on their bandgap. Conductors have overlapping valence and conduction bands, allowing electrons to move freely. Semiconductors have a small bandgap, and insulators have a larger bandgap.

Understanding the bandgap is crucial for designing and optimizing electronic devices. For example, in electronics, materials with specific bandgaps are chosen based on their intended application, such as in the development of transistors, diodes, and other semiconductor devices.

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Presented by Dan Courtney, Three Rivers Community College

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