Use of Anti-Refective Coating

optoex09.in : Use of Anti-Refective Coating

Requires: S-Pisces/Luminous
Minimum Versions: Atlas 5.28.1.R

This example shows how anti-reflective coatings can be simulated in Atlas. This example demonstrates:

  • Construction of simple silicon region
  • Specification of normally incident light beam
  • Definition of anti-reflective layer using the INTERFACE statement
  • Simulation of spectral response

The structure and beam definition sections of this example are similar to other simple examples in this section. The wavelength of the beam will be set on the solve lines, so it is not defined in the beam statement.

The interface statement is used to define optical properties of a coating associated with that interface. A user can define an anti-reflective coating (considered in this example), a dielectric mirror, or an ideally reflecting surface using the interface statement. Note that the coating is not physically present in the structure defined for Atlas. This allows a user to specify certain optical properties while not affecting electrical properties of the structure. The parameter ar.thick defines the thickness of the coating layer. ar.index defines the refractive index of the layer. Most commonly the thickness of a single-layer anti-reflective coating is a quarter of a wavelength (in the material of the coating). For a single-layer coating or for the first layer of a multi-layer coatingi, a user needs to specify the coordinates of the points defining the coated surface p1.x , p1.y , p2.x , and p2.y . If a coating has more than one layer, each subsequent layer must have the number of the coating and the number of the layer specified by parameters coating and layer . Coatings should be specified in order. Layers of one coating should also be specified in order from top to bottom.

If a coating is made of an absorbing material, it is possible to take absorption into account by specifying ar.absorb parameter. Totally reflective coatings are also allowed. The coating will behave as an ideal reflector if ar.index parameter is set to a value > 1000.

The refractive indexes in the structure can be checked using the index.check parameter. This produces output of the real and imaginary index in the silicon as a function of the specified wavelength.

The final plot compares the spectral response of the cases with and without the ARC. Note the increase around 0.6um wavelength for the one-layer ARC. A two-layer coating is capable of reducing the reflectivity over a wide range of wavelengths. In this example the terminal current is not important since we consider a one terminal device with no applied bias. The source photocurrent is the amount of current generated by the light source. available photocurrent is the amount of current absorbed by the semiconductor. Differences between these two are due to reflection, transmission or absorption in non-semiconductor materials. The ratio of available/source photocurrents is often known as external quantum efficiency. This quantity can be plotted using the functions in TonyPlot.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.