Hi,

I was wondering if one could get a physical explanation for the variation of the bandgap of a semiconductor
with temperature and pressure.

Could someone provide an explanation for these please?

Most semiconductors (Si, Ge, GaAs) show a bandgap reduction as temperature increases. Should one visualize
this as occuring due to increased lattice vibration and the resulting reduction in energy required for an electron to
jump from the outer orbitals to the free electron gas in the middle of the gaps, or is the explanation different?
One exception is PbS whose bandgap increases.

Pressure would intuitively seem to do the same, bringing atoms in the lattice closer and reducing bandgap.

Is this really the case?

Thanks & Regards
Vivek