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COMSOLPIN photodiode example simulation (updated)

Posted Mar 8, 2016, 7:31 p.m. EST Low-Frequency Electromagnetics, Semiconductor Devices, Wave Optics, Studies & Solvers Version 5.0 3 Replies

Yuchu He
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Hi, i'm trying to do a photodiode simulation based on the gaas PIN diode example from comsol. In this example, the electromagnetic wave is excited from port1 and port 2 at the semiconductor boundary, with uniform electric field. I made a slight change to the example. Instead of exciting a uniform wave at port 1, now i'm exciting it with a Gaussian field distribution, i.e, Ez=exp(-(x/1000[nm])^2). I've also made some change to the meshing(which works fine if the excitation is uniform). However, i'm getting this error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.ewfd.normE@VDN${realdot@2}
- Defined as: (0.5*((realdot(comp1.ewfd.Ez,comp1.ewfd.Ez)+(realdot(comp1.ewfd.Ex,comp1.ewfd.Ex)+realdot(comp1.ewfd.Ey,comp1.ewfd.Ey)))^(-0.5)))
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.semi.Enorm0_wo@VDN${realdot@2}
- Defined as: ((0.5*((realdot(comp1.ewfd.Ez,comp1.ewfd.Ez)+(realdot(comp1.ewfd.Ex,comp1.ewfd.Ex)+realdot(comp1.ewfd.Ey,comp1.ewfd.Ey)))^(-0.5))))
Failed to evaluate expression.
- Expression: d(((comp1.semi.Enorm0_wo*unit_m_cf)/unit_V_cf),{realdot@2})

anyone has any idea what might be the cause? Thanks a lot!
3 Replies Last Post Feb 22, 2017, 1:49 a.m. EST
Yuchu He
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Posted: 8 years ago Mar 9, 2016, 9:16 a.m. EST
is the negative power of zero due to meshing, convergence, or some other reason?
is the negative power of zero due to meshing, convergence, or some other reason?
Yuchu He
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Posted: 8 years ago Mar 10, 2016, 12:41 p.m. EST
any help would be appreciated, otherwise i probably will switch to TCAD altas to do this, which requires learning the new software...
any help would be appreciated, otherwise i probably will switch to TCAD altas to do this, which requires learning the new software...
Ankit Kumar Pandey
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Posted: 7 years ago Feb 22, 2017, 1:49 a.m. EST

Hi, i'm trying to do a photodiode simulation based on the gaas PIN diode example from comsol. In this example, the electromagnetic wave is excited from port1 and port 2 at the semiconductor boundary, with uniform electric field. I made a slight change to the example. Instead of exciting a uniform wave at port 1, now i'm exciting it with a Gaussian field distribution, i.e, Ez=exp(-(x/1000[nm])^2). I've also made some change to the meshing(which works fine if the excitation is uniform). However, i'm getting this error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.ewfd.normE@VDN${realdot@2}
- Defined as: (0.5*((realdot(comp1.ewfd.Ez,comp1.ewfd.Ez)+(realdot(comp1.ewfd.Ex,comp1.ewfd.Ex)+realdot(comp1.ewfd.Ey,comp1.ewfd.Ey)))^(-0.5)))
Failed to evaluate temporary symbolic derivative variable.
- Variable: comp1.semi.Enorm0_wo@VDN${realdot@2}
- Defined as: ((0.5*((realdot(comp1.ewfd.Ez,comp1.ewfd.Ez)+(realdot(comp1.ewfd.Ex,comp1.ewfd.Ex)+realdot(comp1.ewfd.Ey,comp1.ewfd.Ey)))^(-0.5))))
Failed to evaluate expression.
- Expression: d(((comp1.semi.Enorm0_wo*unit_m_cf)/unit_V_cf),{realdot@2})

anyone has any idea what might be the cause? Thanks a lot!


Please check initial values under Electromagnetic Waves, Frequency Domain study. I faced same problem due to zero (0) value under Electric field for x,y and z. This problem was solved using Ez=1
[QUOTE] Hi, i'm trying to do a photodiode simulation based on the gaas PIN diode example from comsol. In this example, the electromagnetic wave is excited from port1 and port 2 at the semiconductor boundary, with uniform electric field. I made a slight change to the example. Instead of exciting a uniform wave at port 1, now i'm exciting it with a Gaussian field distribution, i.e, Ez=exp(-(x/1000[nm])^2). I've also made some change to the meshing(which works fine if the excitation is uniform). However, i'm getting this error: Attempt to evaluate negative power of zero. - Function: ^ Failed to evaluate temporary symbolic derivative variable. - Variable: comp1.ewfd.normE@VDN${realdot@2} - Defined as: (0.5*((realdot(comp1.ewfd.Ez,comp1.ewfd.Ez)+(realdot(comp1.ewfd.Ex,comp1.ewfd.Ex)+realdot(comp1.ewfd.Ey,comp1.ewfd.Ey)))^(-0.5))) Failed to evaluate temporary symbolic derivative variable. - Variable: comp1.semi.Enorm0_wo@VDN${realdot@2} - Defined as: ((0.5*((realdot(comp1.ewfd.Ez,comp1.ewfd.Ez)+(realdot(comp1.ewfd.Ex,comp1.ewfd.Ex)+realdot(comp1.ewfd.Ey,comp1.ewfd.Ey)))^(-0.5)))) Failed to evaluate expression. - Expression: d(((comp1.semi.Enorm0_wo*unit_m_cf)/unit_V_cf),{realdot@2}) anyone has any idea what might be the cause? Thanks a lot! [/QUOTE] Please check initial values under Electromagnetic Waves, Frequency Domain study. I faced same problem due to zero (0) value under Electric field for x,y and z. This problem was solved using Ez=1

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