Learning Forum

[Mariah Ha]

Hi, 

My question is regarding the silicon material in FDTD. If I am simulating in CHARGE a PIN photodiode, where p layer is silicon doped 10^18 and n lauer is doped 10^19, nd want to simulate the same device in FDTD,do I need to modify the Silicon-Palik material which is available in FDTD? Isit wrong to keep it silicon through p and n layers without modifying the material index?

If I need to create different silicon materials for every silicon layer, do you have any hints how to do so? How do I import the new index for a specific doping value ? 

Thank you. 

Regards.

[Amrita Pati]

Hi Mariah,

I don't think you will be required to change the material of your FDTD simulation based on the CHARGE simulation. In a photodiode, optical energy is converted to electrical energy. So, we first perform the FDTD simulation to calculate the absorption and generation rate in a material when light is incident on it. We export these results to CHARGE to perform the electrical simulation and determine results such as the photocurrent. An example of the approach can be found on the following page: Vertical photodetector.

What you mention here is relevant for other applications such as PIN modulator. The operation of a PIN modulator is based on change in refractive index of a material due to charge injection. In these cases, you can use the np density Index Perturbation to account for the index perturbation of the material from the carrier density. An example is shown here: PIN Mach-Zehnder modulator. 

Regards,
Amrita

[Mariah Ha]

Thank you very much for the clear answer it hrlped me a lot.