The key feature of SRH generation is thermal excitation.
During the recombination process there is no thermal
excitation. Carriers recombine through intermediate G-R
centers. Electrons drop and holes rise in energy. This is a
desired state and recombination proceeds relatively rapidly.
This is not true for generation. A thermally activated process
is very dependent on the temperature and on the activation
energy. We can see this by examining the SRH generation
rate. SRH statistics give the thermal ehp generation rate as