13th WG4 General Meeting
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Europe/Zurich
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The meeting opened at 15:00 and closed at 15:45.
The number of attendees was stable at 17.
General news:
- The next DRD3 week takes place in Amsterdam, 2nd to 6th of June. Abstract submission closes at noon on May 23rd. Please submit abstracts!
- The WG4 session block is scheduled on the Thursday morning (5th of June)
Evridiki Chatzianagnostou presented work on TCAD simulations of 3D silicon sensors
- Studying 3D silicon sensors, investigating the possibility of internal charge multiplication
- Investigating different geometries; fully penetrating or partially penetrating electrodes
- Looking at breakdown behaviour
- Different geometries
- Different p-mechanism geometries
- Investigating modifications of the end of the pillar, adding a "head" which seems to improve gain capabilities
Questions and Answers:
- Gregor K: Similar studies were shown in a previous meeting. How would one go about making this round tip? How can it be etched? EC: FBK didn't immediately object to the idea, it seems possible. It's done using deep reactive ion etching. Martin v.B: Have discussed with Maurizio. Bosch process, isotropic. Colum with a ball on the end.
- Gregor K: How are the doping profiles made? EC: Generic TCAD profiles, using an error function with 1.5 µm for diffusion.
- Marco B: For the simulations using the heavy ion model deposition: how many different locations within a cell are tested? EC: Normally we look in the optimal position, between pillars. It is the best case scenario. Will later go to Allpix Squared to scan over the full pixel cell. Gregor K: It matters a lot where the deposition occurs; the gain is not the same across the cell. This was also seen in our work (see presentation at previous meeting).
- Jürgen B: Why is this approach more radiation resistant? EC: better at maintaining gain than an LGAD, because type inversion does not affect the gain layer. Gregor K: There are two effects. Increasing space charge means more gain, and there is no acceptor removal. JB: The effect of traps will weaken the field. GK: It actually shapes the field. Trapping of charge carriers is the biggest issue. A smaller cell size helps here.
- Håkan W: On p.7-8, the polygon breaks down much later than the circle. There seems to be something a bit odd here. EC: Might be due to how the circular p-stop geometry is created. The Ref/Eval window is tricky for round. Andrei D: I have a script for this, will provide it.
- Jixing Y: Are these simulations based on three-dimensional geometries, and are surface damage models included? EC: Yes, they are three-dimensional, but no surface damage modelling on p.8. Later though. JY: Which surface damage model is used later? EC: Using fixed positive charge in the silicon dioxide.
- Marco B: What's the frequency used for getting the CV curves? EC: 100 kHz. MB: This could be too large to account for the radiation damage properly. Recommend trying 1 kHz or 450 Hz, so the defects have time to be involved.
- Jörn S: There is a silicon PM development using a similar geometry, could be worth having a look at. Tip SiPM or Tip Avalanche Photodiode.
Other updates:
- The 6th Allpix Squared workshop was successfully held last week. More updates will come.
The conveners will announce the time for the next meeting via email.
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