Minibands and Minigaps in Quantum Cascade lasers

[JPLphys]

TL;DR Summary

What is the structure and how are minibands and minigaps in QC Lasers implemented

Summary:: What is the structure and how are minibands and minigaps in QC Lasers implemented

Hello everybody,

I have a question regarding the miniband and minigaps that are displayed widely in diagrams about the functioning of Quantum Cascade Lasers. How are this mini-gaps established physically? And what is there effect?

Thanks in advance

 

[Dr_Nate]

I'm not an expert on quantum cascade lasers, but I understand band structures.

I've looked at some images. Aren't all these diagrams just a series of square wells with an electric potential across them? Thus the gaps are just band gaps in the finite-size material?

If I am correct then this simulation should be conceptually helpful: https://phet.colorado.edu/en/simulation/legacy/band-structure. You can modify the band structure and even apply an electric potential across it.

 

[Fred Wright]

Please see http://www.iue.tuwien.ac.at/phd/moradinasab/dissse2.html.
In the following excerpt SL refers to Superlattice and QW refers to Quantum Well.

"In general, semiconductor SLs consist of a periodic stack of nanometer-thick layers of QWs and barriers. The period of this artificial crystal is typically much larger than the lattice constant of the bulk crystalline constituents. This superimposed periodic crystal potential splits the conduction band (and the valence bands as well) along the direction normal to the layers into a series of narrow (typically, tens to a few hundreds of meV wide) minibands separated by energy gaps (’minigaps’) in the strong-tunnel-coupling regime. For a given set of materials, miniband and minigap widths can be engineered by suitable choice of the layer thicknesses. In the generic case of the simple periodic SL, however, those widths are not independent of each other [108]. "

 

[JPLphys]

Thank you very much, the both of you. You have helped me a lot.