Direct and Indirect Optical Band Gap

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Discussion Overview

The discussion centers around the concepts of direct and indirect optical band gaps, including inquiries about equations related to their calculation and the differences between these types of band gaps. The scope includes theoretical aspects and potential applications in solid-state physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks an equation to determine the values of direct and indirect optical band gaps, expressing uncertainty about the definitions and differences between them.
  • The equation Eg=hω/λae is mentioned, with Eg representing the optical band gap and λae the wavelength at the absorption edge, prompting a request for clarification.
  • Another participant notes the relevance of the question to atomic, solid state, and computational physics, suggesting a more appropriate forum for the topic.
  • A different participant draws a comparison to direct versus indirect bandgap semiconductors, mentioning the characteristics of silicon as an indirect band gap semiconductor and its implications for photon emission.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the definitions or equations related to optical band gaps, and multiple viewpoints regarding the relevance of the topic to different physics subfields are presented.

Contextual Notes

The discussion lacks specific definitions of direct and indirect optical band gaps, and the assumptions underlying the proposed equation are not fully explored. There is also a mention of the need for phonons in the context of indirect band gap semiconductors, which remains unaddressed.

Donchay
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I've been looking on journals and textbook, as well as internet. Does anybody know if there is an equation to find out the value of direct optical band gap and indirect optical band gap? What is the difference of optical band gap, direct optical bandgap and indirect optical bandgap?

also

Does anybody recognised this equation

Eg=hω/λae

where Eg= optical band gap , λae= wavelength at absorption edge

Please enlighten me.

Thanks.
 
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This question is more apt for the atomic, solid state and computational physics forum.
 
this is reminiscent of direct bandgap vs indirect bandgap semiconductors ...

The energy bands are plotted in momentum-space and look like wavy lines
Good explanation and examples are shown here

http://www.doitpoms.ac.uk/tlplib/semiconductors/direct.php

Silicon is an indirect band gap semiconductor with a 1.1 eV bandgap width; it is too narrow to emit in the visible and also indirect, which requires a also phonon if an infrared photon is to be emitted.
 
Thread has been moved.

Zz.
 

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