Questions on Graphene PIN Junction Simulation

Hi Ahsan,

I have a few questions regarding simulation for Graphene PIN junction(see attached). Graphene is on the top of silicon PIN Junction. Bias from 0~8V is added to the metal to see some parameters(band structure, Electric field, charge). In simulation, I have some questions which I’m not sure.

  1. In the Charge Solver, there is an option for Small Signal AC. What does it mean for the frequency option? How to set those values in the Small Signal AC option? How could the Small Signal AC setting affect the simulation results?

  2. In simulation structure of the attached file, the minimum length is 1nm which is the height of graphene. In the Global Mesh Constraints in Charge solver, I set min edge length to be 0.5nm which is smaller than the minimum length in the structure. Does that make sense?

  3. In DEVICE, if I open the Electric Field option in the Monitors, after I run simulation, the result is Electrostatics? When I tick the save data option and determine the file name, after I run the simulation, there isn’t matlab file(.mat) saved in my original folder, I don’t know why.



SiG_PINjunction_0_8VBias_MOD_1nm_Zchange _250nm_layout.ldev (6.4 MB)

For a quick description of all the input parameters of the small-signal parameters take a look at this KB page ( Simulation - CHARGE). The three frequency options allow you to choose the frequencies at which you want to run the small signal analysis.

Making the value of the min edge length smaller that the smallest dimension in your simulation makes sense. However in this particular case since the graphene layer is so thin, making the min edge length smaller than that might lead to unnecessarily small mash in some other places. An alternative could be to use a larger value for the min edge length in the global setting and then use a mesh override over graphene only where you can set the edge length limit to 0.5 nm.

The electric field monitor that you have in your file is a 3D monitor while your simulation is a 2D simulation. Unlike FDTD when you have a 3D monitor in a 2D solver the solver simply ignores the monitor. You will have to use a 2D monitor (simply change the monitor type in the monitor properties) to be able to record the electric field from your simulation.

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Hi Alam,

I encounter a new question on this project.

The lumerical file has been uploaded here
(A ldev file, one band structure Ec distribution on the cross-section of graphene-silicon pin junction, two E field distribution diagrams (Ex, Ez) on the cross-section of graphene-silicon pin junction, these diagrams are processed and generated from the matlab after exporting band structure and E field data from lumerical DEVICE solver)

The model is similar with the one before, a graphene-silicon pin junction. Graphene is on the top of silicon pin junction. Now I added some vias (material: etch) from the top to the bottom of silicon pin junction, in the center region of silicon pin junction. And I simulated to see how the E field and band structure vary under different bias from 0-8V.

  1. Normally, for the cross-sectional view of E field and band structure distribution, due to the etch vias, should the E field and band structure vary or reveal difference on the region of the vias? But as the simulation results shown, there’s no significant sign or change on the region of the vias for both E field and band structure distribution.

  2. Could you help me check on the model? Is there anything wrong with my model? I set the vias with mesh order 1 prior than the silicon pin junction with a mesh order 2. Does the software consider the effect of vias when simulating the structure? If so, why there’s no any signs or changes on the region of the vias for both E field and band structure distribution?

Thank you so much and looking forwards.