RATRO적용방법에 대한 첨부 엑셀파일 참고하시기 바랍니다.

RATRO make ray-tracing ONLY inside the computational domain consisting
of the following three blocks: substrate, n-semiconductor layer, and
p-semiconductor layer. All other features like electrodes, pads,
spreading and blocking layers are treated just as different boundary
conditions between the surface of the computational domain and the
immersion medium.

Let us consider p-GaN covered by 10 nm Cr electrode and then by 200 nm
Au pad. Please see the attached file which is slightly modified Planar1
example.

Keeping in mind that p-electrode is always inside p-semiconductor, and
p-pad is always inside p-electrode, we can say that there are three
possible states for the p-side:

- free surface of p-GaN ("p-semiconductor" surface)
- surface covered by p-electrode only ("p-electrode" surface)
- surface covered by both p-electrode and p-pad ("p-pad" surface)

For each of these surfaces, one can specify COMPLETELY independent
optical settings. So, using "Multiple Layer" option for p-pad, one have
to include both p-electrode layer and p-pad layer.

IMPORTANT! One need not understand specification of "p-electrode" and
"p-pad" surfaces as specification of material and thickness of the
respective LAYERS. Instead, one need specify COMPLETE optical conditions
for the respective area, including all the underlying layers.

Next, let move to the case where p-electrode and the p-pad have the same
area. Then there are only two possibilities for the p-side surface,
described by settings for "p-semiconductor" and "p-pad" surfaces. The
settings for "p-electrode" surface has NO effect on the simulation
results, because they are not used since there is NO are which is
covered by p-electrode, but not covered by p-pad.

Of course, the same considerations may be applied to n-electrode and
n-pad. Generally, to see the effect of changing the n-electrode
material, one need change both "n-electrode" and "n-pad" settings. If
n-electrode and n-pad have the same area, it is enough to change only
"p-pad" settings.

Next, if the structure includes p-blocking layer, the situation becomes
a little bit more complex, but the principle is the same. One need
determine the relation between the parts of p-side surface and available
surface types. For instance, "p-pad" means the area covered by p-pad,
p-electrode, and p-spreading layer (if any), while "p-pad p-blocking
layer" is the surface covered by p-pad, p-electrode, p-spreading layer
(if any), and p-blocking layer.

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1. As n-electrode has the same area as n-pad, the only necessary setting
for n-electrode and n-pad area is "n-pad" surface.

2. As p-electrode has the same area as p-pad, the only necessary setting
for p-electrode and p-pad area is "n-pad" surface