Help: What is Band-Edge and Near-Band-Edge Emission?

[maxxlr8]

I understand that in photoluminescence band edge emission in direct band gap semiconductors originates from the recombination of electron and hole in the edge of conduction and valence bands. However, recently I have stumbled upon near-band-edge emission, which seem to suggest the existence of other levels. My question is:

1. Is the level in the forbidden band?
2. How does this level exist?

Thank you

 

[Dr. Ahmed Galal]

Near band edge emission may arise essentially from excitonic or other shallow trap states