Transform Edge model to Node model for the Schottky image force and Poole–Frenkel effect

[chenq...@gmail.com]

Hello Juan:

I want to create the image fore model for Schotty contact and detrapping process based on Poole–Frenkel effect. In both models, the height of the potential barrier is varying with the intensity of the electric field. While assembly these effects in the Gaussian Equation of Devsim, the charge intensity at contact and in traps are node models. So I want to know whether there is a method to transform Edge model of electric ield to Node model. 

Poole_frenkel effect

In the image force model, the potential offset is varying with the electrical field at contact. I can solve the equation on the side of the semiconductor,  but for the other side, I can't find the approach to apply the varying potential lag induced by different regions. You advise me of custom_equation to solve this issue. I think it may hard to 

construct custom _equation. 

In my device structure, the source and drain contact is located on one of corresponding 

interface. The equation of the interface is "equation="Potential@r0-Potential@r1"". So is it possible to apply the property of contact on an interface, like the integration of current?

Regards,

QS C

[Juan Sanchez]

Hello,

Currently, it is not possible to integrate current at an interface.
There are conflicting boundary conditions for having overlapping
contacts and interfaces.

With this pre-release:
https://github.com/devsim/devsim/releases/tag/v1.5.0-rc1

I have improved the abilities of the "custom_equation" command to
allow enforcing boundary equations with the custom matrix assembly. I
have also added some additional "contact_equation" options for
treating edge and element based nodal integration.

Please see "doc/devsim.pdf" for the release notes describing the changes.

The example:
examples/diode/diode_1d_custom.py

demonstrates using "custom_equation" to enforce boundary conditions by
directly accessing the matrix and the rhs for the simulation. A
similar approach can be used to set the potential in the insulator to
that in the semiconductor at the same node coordinates.

My suggestion for the insulator-semiconductor boundary is to keep the
Schottky contact on the semiconductor and create a contact on the
insulator.

Then set all of the contact_equation components on the insulator to 0,
which allows you to fill in your own boundary condition with the
custom matrix assembly..

Then use custom matrix assembly to enforce the potential from the
semiconductor side onto the insulator side. There are a few commands
which make it easy to identify the coincident nodes on both sides of
the interface and apply the appropriate equations.

For the "contact_equation" command, I have added these additional options:
edge_volume_model (for edge models)
volume_model (for element edge models)

which makes it possible to treat an edge model on the contact for
volume integration at the contact node. Keeping an edge based
approach is important so that the electric field is full coupled to
the nodes off the contact. In the general case, the electric field on
the element would need to be projected in a direction normal to the
interface, the "volume_model" option may be in order.

I suggest isolating the components dependent on the electric field and
keeping the other components the same on the "contact_equation"
command. The electric field based nodal components could then be
handled using a "volume_model" that will be assembled in terms of the
electric field and the nodal components at each end of the edge.

This is just an outline, and would require a bit of effort to get working.

Regards,

Juan

On Sat, Jan 2, 2021 at 9:01 AM chenq...@gmail.com <chenq...@gmail.com> wrote:
>
> Hello Juan:
>
> I want to create the image fore model for Schotty contact and detrapping process based on Poole–Frenkel effect. In both models, the height of the potential barrier is varying with the intensity of the electric field. While assembly these effects in the Gaussian Equation of Devsim, the charge intensity at contact and in traps are node models. So I want to know whether there is a method to transform Edge model of electric ield to Node model.
>

> Poole_frenkel effect
>
> In the image force model, the potential offset is varying with the electrical field at contact. I can solve the equation on the side of the semiconductor, but for the other side, I can't find the approach to apply the varying potential lag induced by different regions. You advise me of custom_equation to solve this issue. I think it may hard to
> construct custom _equation.
>
>
> In my device structure, the source and drain contact is located on one of corresponding
> interface. The equation of the interface is "equation="Potential@r0-Potential@r1"". So is it possible to apply the property of contact on an interface, like the integration of current?
>
> Regards,
> QS C
>

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