How ionization energy can be lower than band gap?

In summary, the conversation discusses the observation that for Silicon, the ionization energy is lower than its band gap energy, which is confusing to the person reading about ionization energy in semiconductors. They question if this is for the ionization energy of an electron in the conduction band and why it is problematic. Another person clarifies that this is a bulk effect and not just near the surface, and asks if the person is reading a paper from before 1985. The original person confirms they were reading a book and thanks matterwave for the clarification.
  • #1
newuser
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0
I am reading about the ionization energy in semiconductors and came across this thing that for Silicon, the ionization energy is lower than its band gap energy. I don't understand how can this be?
 
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  • #2
Is this for the ionization energy of an electron in the conduction band? It seems to me that there should be no problem having an ionization energy lower than the band gap. Why do you find it problematic?
 
  • #3
Well that makes sense. The book does not says it explicitly so I guess what you say is the case.
 
  • #4
I thought that was only the near the surface and when treated with a special coating. E.g. Ce on GaAs. I didn't think it was a bulk effect too. Are you reading a paper from before 1985? The history of semiconductors has a lot of back and forth.
 
  • #5
@ rigetFrog: I was reading the book. The answer given by matterwave is correct. I has a silly confusion which is clear now.
 

1. How is it possible for ionization energy to be lower than band gap?

There are a few reasons why ionization energy can be lower than band gap. One possible explanation is that the energy levels of electrons in a material are not always evenly distributed, resulting in some electrons having lower energy levels than others. Another factor could be the presence of impurities in the material, which can affect the energy levels of electrons. Additionally, the band gap is a theoretical concept and does not always accurately reflect the true energy levels of electrons in a material.

2. Can ionization energy ever be higher than band gap?

Yes, in some cases ionization energy can be higher than band gap. This can happen if there are defects or imperfections in the material that change the energy levels of electrons, or if the material is under high pressure or in a high-energy state.

3. How does the concept of band gap relate to ionization energy?

Band gap and ionization energy are both related to the energy levels of electrons in a material, but they represent different aspects. Band gap refers to the energy difference between the highest occupied energy level and the lowest unoccupied energy level in a material, while ionization energy measures the amount of energy required to remove an electron from an atom or molecule in a gas phase.

4. What are some real-world applications of materials with lower ionization energy than band gap?

Materials with lower ionization energy than band gap can be used in a variety of applications, such as in solar cells, where they can efficiently absorb light energy and convert it into electrical energy. They can also be used in LED lights, as the lower ionization energy allows for easier electron movement and therefore, the production of light. Additionally, these materials can be used in transistors and other electronic devices.

5. Are there any drawbacks to having lower ionization energy than band gap in a material?

While there are many advantages to having lower ionization energy than band gap in a material, there are also some potential drawbacks. For example, these materials may be more prone to defects and impurities, which can affect their performance. Additionally, they may have a shorter lifespan compared to materials with higher ionization energy, as the lower energy levels of electrons can lead to easier degradation over time.

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