Known Physics Lacking in Existing Model

  There is significant room for improvement of our current model of CCD response. Some of the device physics that needs to be incorporated into the model is well understood, and it is only a matter of implementation (although, it might be nontrivial from the programming point of view). Among these items are:

1. Near edge absorption structure.

The variation of absorption coefficients in the vicinity of the absorption edges have been measured with a high precision (see Subsection 4.6.3), but not yet incorporated into the model. This will significantly improve the fidelity of the model at near-edge energies.

2. An accurate model of the transition region between depleted and undepleted bulk.

It is generally assumed that there is a sharp transition between depleted and undepleted bulk of silcon. In fact this is not true, since it implies that the concentration of holes changes abruptly at the border. We have developed an accurate solution for this region, its implementation will improve the fidelity of the modeling of the event distribution between different grades.

3. Low energy tail physics.

We have achieved significant progress in understanding the charge splitting at the interface between silicon and SiO₂. This phenomenon is responsible for the shape of the low energy tail of the CCD response function, and we are able now to describe this shape reasonably well. Incorporation of this newly discovered physics into the main CCD model will help to much better predict the shape of the low energy tail.

4. Modeling of traps in the transfer channel.

A lot of effort had been devoted to studies of the radiation effects on the CTI, and general understanding is achieved. Displacement damage creates traps in the channel of the CCD and these traps deteriorate the CTI of the device. The details of traps interactions with signal charge yet have to be put into the model in order to simulate device performance under irradiation.