Question

The energy required to break the covalent bond in a semiconductor is:

• A. always 1 eV
• B. equal to the forbidden energy gap of semiconductor
• C. equal to Fermi energy
• D. much less than Fermi energy

Hint:

In semiconductors, conduction starts when electrons cross the band gap — so bond energy = band gap energy.

Answer 1

The Correct Option is B

To solve this question, let's look at the fundamental concepts related to semiconductors and energy levels.

A semiconductor is a material with an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its conductivity increases with temperature.

The covalent bonds in a semiconductor like silicon or germanium require energy to be broken so that electrons can become free to conduct electricity. This energy corresponds to the energy required to break the bond, which is the energy difference between the valence band and the conduction band. This energy difference is known as the "forbidden energy gap" or "band gap" (Eg) of the semiconductor.

Now, let's analyze the given options one by one:

1. Always 1 eV: This is incorrect. The energy required to break the covalent bond varies depending on the semiconductor material.
2. Equal to the forbidden energy gap of semiconductor: This is correct because the energy required to free an electron from a covalent bond is essentially the same energy as the band gap.
3. Equal to Fermi energy: This is incorrect. The Fermi energy is related to the energy level at absolute zero temperature, which is not directly related to breaking a covalent bond.
4. Much less than Fermi energy: This is incorrect. The bond energy and band gap are specific to material properties and are not necessarily 'much less' than the Fermi energy.

Therefore, the correct answer is that the energy required to break the covalent bond in a semiconductor is equal to the forbidden energy gap of the semiconductor.