[ace2358]

I would agree. Having said that I still think it was a bit wishy washy. The whole treatment of band gap energies I think is quite complicated beyond the simple diagram shown.

[pfdietz]

Also, I don't think the explanation for silicon was correct. As I understand it, the problem with Si is not that the bandgap is in the infrared, it's that it's an indirect bandgap semiconductor which suppresses emission of photons. Instead, the energy of recombination goes into heat.

[ace2358]

Thanks yes I think I remember my whole semiconductor education to be wishy washy (according to the lecturer) even at the undergrad level. Pretty complicated stuff and I think the ‘band gap’ model is a bit of a stretch of the quantum mechanics that is occurring.