kaps_nit
Member level 2
Im facing problems in realizing the meaning of recombination current.....
As we start with the conductiviy property we find that electrons with higher energy moves to conduction band(e- gains energy from thermal or optical excitation). And only conduction band electron offers conductivity in general. Valance band electrons are not responsible for conductivity.
We also know that when recombination takes place, e- from conduction band comes down to valance band and recombines with holes and thereby give off energy as photons.
I referred to Millman Halkias, there also it is clearly written, that in recombination process e- moves to valance band and recombines with a hole and hence a mobile EHP disappears. And the condition for that is, these two elements should have the same momentum with opposite sign.
Now, take the case of transistors, say an npn transistor, here in the active region e- flows from emitter to base region and few of them gets recombined with holes, and leaves the base region as recombination current.
Now how to justify this apparent contradiction, as in this case e- in the valance band contributing in the conduction??????
As we start with the conductiviy property we find that electrons with higher energy moves to conduction band(e- gains energy from thermal or optical excitation). And only conduction band electron offers conductivity in general. Valance band electrons are not responsible for conductivity.
We also know that when recombination takes place, e- from conduction band comes down to valance band and recombines with holes and thereby give off energy as photons.
I referred to Millman Halkias, there also it is clearly written, that in recombination process e- moves to valance band and recombines with a hole and hence a mobile EHP disappears. And the condition for that is, these two elements should have the same momentum with opposite sign.
Now, take the case of transistors, say an npn transistor, here in the active region e- flows from emitter to base region and few of them gets recombined with holes, and leaves the base region as recombination current.
Now how to justify this apparent contradiction, as in this case e- in the valance band contributing in the conduction??????