What happens after I give energy more than forbidden gap

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Discussion Overview

The discussion centers around the behavior of silicon, a semiconductor, when subjected to energy inputs exceeding its forbidden energy gap of 1.1 eV. Participants explore the implications of applying an electric field and the effects of high energy on the covalent bonds within silicon, including the potential for avalanches and the state of the material post-energy application.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions what happens when energy greater than the forbidden gap is supplied, suggesting that only a few electrons may transition to the conduction band due to varying bond strengths in the valence band.
  • Another participant introduces the concept of electric fields and their role in electron movement, mentioning that high fields can lead to tunneling and avalanches from existing electron/hole pairs at room temperature.
  • A participant seeks clarification on the aftermath of avalanches, questioning whether all covalent bonds in silicon would break and how the material would behave post-avalanches.
  • It is noted that breaking all bonds could theoretically reduce silicon to isolated atoms, but this is challenged by another participant who asserts that electronic effects primarily affect a small subset of electrons and do not alter the overall crystal structure significantly.
  • Discussion includes the impact of extreme conditions, such as intense laser pulses, which may vaporize material and bypass traditional band structure considerations.

Areas of Agreement / Disagreement

Participants express differing views on the extent of bond breaking and the overall impact on silicon's structure. There is no consensus on whether all covalent bonds would break during avalanches or how the material would recover afterward.

Contextual Notes

Participants mention specific temperature thresholds, such as the melting point of silicon, and the conditions under which avalanches occur, indicating that the discussion is limited by assumptions about temperature and energy levels.

Who May Find This Useful

This discussion may be of interest to those studying semiconductor physics, materials science, or electrical engineering, particularly in the context of energy applications and semiconductor behavior under extreme conditions.

Ahsan Khan
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Hello guys I have a question about semiconductor, suppose I have a semiconductor say silicon at room temperature. The forbidden energy gap in case of Silicon is 1.1eV. Suppose I give I introduced an electric field(or by any other way give energy) which could give each electron an energy more than 1.1. What will happen then?

I suspect with an energy of say 1.2eV only few(relatively) electrons will go to conduction band breaking the valence bond. Because for other electrons in valence band the gap will be even more than 1.1eV. As forbidden gap is defined as the difference between highest energy level of valence band and lowest (available) energy in conduction band. So it should not take equal energy to take electrons from the different valence bond . in other words it would take different energy to break different bonds. Am I correct? My other question is what will happen if I give very high amount of energy so that I am successful in breaking all the bonds between silicon atoms? Will it reduces to isolated atoms then?

Regards
 
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An electric field is energy per distance for electrons, electrons that cannot move have problems to "use" the electric field. Very high fields allow direct tunneling, but long before that you get avalanches from individual electron/hole pairs that exist at room temperature.
ovais said:
My other question is what will happen if I give very high amount of energy so that I am successful in breaking all the bonds between silicon atoms? Will it reduces to isolated atoms then?
If you heat silicon, it will melt and then boil, sure.
 
mfb said:
An electric field is energy per distance for electrons, electrons that cannot move have problems to "use" the electric field. Very high fields allow direct tunneling, but long before that you get avalanches from individual electron/hole pairs that exist at room temperature.
Thank you :) Sorry I wrote in a an unclear way, we'll what I want to know, what will happen after Avalanches, will all the covalent bonds break? Of yes how will the Silicon as sold sustain with all bonds broken? Breaking all bonds should reduce silicon solid into isolated atoms or something.

In short I want to know what is the state of Silicon during Avalanche in terms of free electrons in it and the states of most of its covalent bond.

I also want to know how will things become after removal of electric field from an Avalanched silicon again in terms of free electrons in it and the state of most of its covalent bonds. Will it recover from all of its broken bonds and become same as it was before it gone through Avalanche?

mfb said:
If you heat silicon, it will melt and then boil, sure.

What is meant is to heat to 900 °C given its melting point is above 1400°C.
 
Those electronic effects happen with a tiny subset of the electrons in the material, they don't influence the crystal structure as a whole.
Silicon with avalanches is still a silicon crystal, just with some current in it.

Extremely intense laser pulses are an exception, where you can vaporize some material directly. There the band structure does not matter any more.
 

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