52
Figure 5.6: The bandgap of the heterostructure as a function of n and n.
Each rectangle in the plot represents a compound with the stacking sequence
nm. The figure is taken from the Paper-4.
states are analyzed. In Figure 5.8 the wavefunctions of the VBM and CBM
states are plotted for and 2. The figure shows that the VBM mainly
consists of the N2p orbitals in both and 2 and is located in the region
of the heterostructure. Additionally, calculations also suggest that the along
with the character the position of the VBM state also does not change relative
to low-lying level for the different structures, therefore, it can be safely
assumed that it is only the nature and position of the conduction band which
is responsible for the bandgap variation in n. It can also be seen that in
the CBM states are located in the TaON plane and mainly consists of the Ta
d orbitals. Therefore, in order to see if the same trend is followed in n as
the number of layers is increased the weights of the CBM state is analyzed.
The Figure 5.9 shows the planar average (xy plane) of the weights of the CBM
state in the real space. The area of the circle represents the magnitude of
the weight for the different planes stacked along the z-direction. The boxes
represent the unit cell and the dotted lines the interface between the and
layers. As expected the CBM state is mainly comprised of the Ta d orbitals
and located on the TaON plane. The figure also shows that as the number of
layers is increased the CBM states become less confined therefore resulting