Why the mass action law is not valid for very low temperatures?

[Ger3]

why the mass action law is not valid for very low temperatures??

Hi,
In the context of semiconductors, I was asked why the mass action law is not valid for very low temperatures. I thought that it was valid, since for very low temperature it holds the non-degeneracy condition $$E_g >> k_B T$$ (I think so...). But maybe for some other reason it breaks. Does someone know why? Thanks!

 

[hjelmgart]

I am not sure, but perhaps it is related to the behavior of electrons in the lattice, which becomes more prominent at lower temperatures (or low energies)?