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layers and for two layers it is mainly the tunneling effect responsible for the
bandgap variation. Therefore, it can be expected that if the number of layers
is increased while keeping the number of layers constant the variation of the
bandgap would be an interplay between the confinement and the tunneling
effect. In order to see this effect the Figure 5.11 shows similar plot as Figure
5.9 & 5.10 with the difference that the number of layers is fixed to one while
the number of layers is increased. The behavior for and 2 is already
shown in the Figure 5.9 & 5.10. In going from 2 to 6 the tunneling as well
as confinement decreses. However, the decreased tunneling has the opposite
effect as the decreased confinement i.e as the tunneling decreases the bandgap
increases as in Figure 5.10 whereas the decreasing confinement decreases the
bandgap as in Figure 5.9. These two competing effects results to a minima
in the bandgap for the for a particular number of layers. The Figure 5.11
shows that up to 4 layers the confinement effect dominates thus leading to
the bandgap reduction in moving from 2 to 4, however, in going from 4
to 5 the diminishing tunneling dominates over the decreased confinement
thus result in an increase in the bandgap. The above analysis for different
Figure 5.11: Similar plot as in 5.9 with the difference that the number of
layer is fixed to one and the number of layer is varied. As the number of
layer is increased beyond 2 the tunneling and confinement effect compete
with each other result in decreasing of the bandgap up to 4 and then the
increase of the bandgap. The figure is taken from the Paper-4.