Spatial separation of generation and
recombination
A different situation occurs if the generation is choosen inhomogeneously. The left part of the figure shows the current distribution In (x) for different constant currents I with the generation
near the positive contact. Because of the sensititvity of the potential modulation to excess carriers, the potential
modulation starts to be reduced in the illuminated area and therefore at the same time a lateral potential gradient
arises which distributes the excess carriers all over the sample area very fast. This quick lateral transfer is well
known as the enhanced ambipolar diffusion, which is implicitely included in the model. Due to this fast transfer the
carriers can recombine in the whole sample area if no external current is supplied. The current in the n-layer then is
dominated by this transfer current (lowest trace in the figure ). If the generation
area is kept fixed near the positive contact and the external current is increased, the potential modulation is also
increased near the positive contact because of the voltage drop within the n-layer. The current redistribution still
takes place but no recombination is possible in that region because of the enlarged potential modulation.
Consequently the sample area for recombination is shrinking more and more to a region near the negative contact.
There the potential modulation has to be reduced in order to keep the balance of total generation and
recombination.
If the inhomogeneous generation is in an area near to the negative contact (right part of the figure ) the situation is opposite as discussed above: With increasing current the recombination
is more and more located at the same site of the sample as the generation, near the negative contact. Therefore no
current transfer is required and the area without generation remains nearly unaffected.
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