Energy Band Diagram Of Intrinsic Semiconductor

When an electrical charge is passed through a semiconductive material, the electrons in the atom gain high energy levels, break away from the atom’s rotational orbit and become free-flowing electrons. The space left behind by the free electrons in the atom orbit is known as a hole. In an intrinsic semiconductor, the number of electrons in free motion outside the valence band of an atom is equal to the number of holes in the valence band. The existence of an energy band diagram can help us successfully compute the energy levels of an intrinsic semiconductor.

Intrinsic Semiconductor

They are poor conductors of electricity as they allow very limited, sometimes no passage of electricity through them. They are mostly used as insulators. This example of intrinsic semiconductors exists as there are an equal number of electrons and holes in the atomic structure of these elements. The free electrons form covalent bonds with other atoms to create stable electrical conductivity. This is better explained through the energy band diagram of an intrinsic semiconductor that shows the distribution of electrons and holes in an intrinsic conductor.

The Energy band diagram

An energy band diagram measures the energy levels displayed by free-flowing electrons in semiconductors. The energy level of an electron is measured against its movement through different objects or solid states in the X-Y axis diagram. This diagram is dependent on the movement of the electron and can not be measured in terms of the stationary electron. In the study of semiconductors, the presence of holes is also acknowledged in the energy band diagram of an intrinsic semiconductor.

The energy band diagram of intrinsic semiconductors always displays the same quantities of electrons and holes and is considered the most stable semiconductor. The space between the electrons and holes in the diagram always remains constant in an intrinsic semiconductor.

Energy Band Theory

In 1927, Walter Heitler and Fritz London discovered that different frequencies in energy levels of free-flowing electrons are created as the material moves through different forms of mass and temperature. The study of these differences or bands defined the energy band theory and further led to the discovery of the energy band diagram. There are three bands of energy primarily considered.

1. Valence Band – The electrons that are securely tied to the orbit of an atom are known as valence electrons. They possess properties of stability and low electrical conductivity.

2. Conduction band – When exposed to higher levels of electrical charge, some of the electrons in the valence band gain high amounts of energy and can break through the band and become free electrons. These electrons will combine with other atoms or groups of atoms and create a smooth flow of electricity. So they are unstable in form and are high conductors of electricity.

3. Forbidden gap – The space between the valence band and conduction band is the forbidden gap. This contains no electrons, so no energy levels and the size of the gap determines the conductive properties of the element. In an energy band diagram of intrinsic semiconductors, the gap is almost always equal when electricity is passed through it.

Classification of energy band diagrams

As we discussed in the previous section, there are three basic components of an energy band diagram. This energy band can be explained on two bases of classification.

1. Bias/ No bias – This is the classification based on the amount of voltage exposed to the material of the semiconductor.
   The first reference to an energy band diagram is an intrinsic semiconductor where the energy level lies exactly in the middle of the conduction band and valence bands. The energy level lies close to the conduction band in an extrinsic semiconductor. And the third type shows the energy level closer to the valence band.
   
   
   

2. Dope/ undoped – This determines if the semiconductor was formulated chemically or exists in nature in a true form. This can be further studied as doped, heavily doped, or undoped.

Silicon and Germanium are two prominent examples of intrinsic semiconductors.

Conclusion

An intrinsic semiconductor can produce limited number amount of electrical discharge. They are mostly used as insulators or protection from electrical conductors. This can be highly affected if the intrinsic semiconductor is exposed to high heat levels. It can generate electrical current, destroy adjacent objects, or cause fire and explosions. The energy band diagram of intrinsic semiconductors helps us understand the amount of energy released in different intrinsic structures based on the amount of heat released.