Source: Energy Education

The Band Gap in Semiconductors

Understanding the Band Gap

The band gap in semiconductors refers to the minimum energy required to move an electron from a bound state to a free state where it can conduct electricity. It is a crucial property that determines the material’s ability to conduct and generate energy.

Band Structure of Semiconductors

The band structure of a semiconductor is represented by a band diagram, where the energy levels of electrons are plotted on the y-axis. The valence band (E_V) represents the lower energy level where electrons are bound, while the conduction band (E_C) is the energy level where electrons are free to conduct.

Role of Band Gap

The band gap (E_G) is the energy difference between the valence band and the conduction band. It signifies the minimum energy needed to excite an electron for conduction. Once excited, the electron can move freely in the semiconductor and participate in conduction processes.

Generation of Carriers

When an electron is excited to the conduction band, it leaves behind a hole in the valence band. This hole can also participate in conduction, creating what are known as carriers. The movement of these carriers through the crystal structure enables the flow of electricity in the semiconductor.

Concept of Holes in Semiconductors

The concept of a hole in a semiconductor is similar to a bubble in a liquid. While it is the electrons that move, it is easier to visualize the movement of the hole in the opposite direction. This movement of holes and electrons collectively contributes to the conductivity of the semiconductor.

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