uploading APD example

[FilipeFcp]

Hi all,

I’ve added some text and the image.
The mode simulation looks good, I ran a few tests, and the results seem quite solid. It’s a bit different from what’s shown in the paper, but if I understood correctly, they simulate the coupling from the Si waveguide into the Ge region. Nevertheless, the results for the photocurrent appear consistent.

The main discrepancy occurs around 11 V, which seems to correspond to the breakdown voltage. But I couldn't figure out why.

[github-actions]

Spell Check Report

AvalanchePhotodiode.ipynb:

Cell 2, Line 1: 'Photodiode'
  > # Avalanche Photodiode
Cell 2, Line 3: 'photodiode'
  > This notebook demonstrates the modeling of an on-chip avalanche photodiode (APD).
Cell 2, Line 13: 'band-to-band'
  > We will define both the optical and charge properties of the materials, including doping, and models for band-to-band tunneling and impact ionization.
Cell 10, Line 8: 'ymin'
  > source="ymin",
Cell 10, Line 27: 'ConstantDoping'
  > # p_Ge = td.ConstantDoping.from_bounds(concentration=1e18, rmin=(-ge_b_w, si_b_h+si_t_h-s_ol, -z_size), rmax=(ge_b_w, si_b_h+si_t_h+ge_h+s_ol, z_size))
Cell 12, Line 14: 'Nunley'
  > optical=td.material_library["Ge"]["Nunley"],
Cell 21, Line 8: 'x-size'
  > # Cross-section simulation (x-size=0), periodic bc OK for mode extraction

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Checked 1 notebook(s). Found spelling errors in 1 file(s).
Generated by GitHub Action run: https://github.com/flexcompute/tidy3d-notebooks/actions/runs/19183204843

[tomflexcompute]

Thanks @FilipeFcp and @marc-flex on making this possible. A few comments:

1. "Photodiode" on the title -> "photodiode"
2. In the beginning, add a brief overall introduction about avalanche photodiode
3. This is more for @marc-flex , can we add some convenient functions to calculate the optical absorption to reduce the codes in cell[12]?
4. Explain a little bit on the physics of dark and bright currents as well as what the final result implies.

[marc-flex]

Thanks @FilipeFcp for turning my draft into this nice notebook! I left some minor comments (most of which are my fault to begin with). It'd also be good if @momchil-flex could have a quick look

• In cell 2 I left a T0 = 280. I think it is safe to just use 300. Either way we should probably only leave 1 to avoid confusion.
• In cell 3 maybe remove comments (e.g., alpha_n_inf=7.03e5/8000,) that I used to try things out. Actually, I left a lot of comments scattered throughout the notebook. So sorry about it
• in cell 20 I'd change the comment to say that we're only visualizing the x component of the electric current. As an alternative we could compute the modulus of the current density vector and plot that instead?
• In cell 21 maybe add label for the x axis? i.e., applied bias

[marc-flex]

This is more for @marc-flex , can we add some convenient functions to calculate the optical absorption to reduce the codes in cell[12]?

We should definitely think of something, especially as we add more other effects such as the TPA that @momchil-flex has been working on.