Direct and Indirect Optical Band Gap

[Donchay]

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

E_g=hω/λ_ae

where E_g= optical band gap , λ_ae= wavelength at absorption edge

Please enlighten me.

Thanks.

 

[DrDu]

This question is more apt for the atomic, solid state and computational physics forum.

 

[Sunfire]

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.

 

[ZapperZ]

Thread has been moved.

Zz.