Offer support towards the implementation of TPA-TCT systems and contribute to the evaluation of newly developed sensors technologies

The Two Photon Absorption - Transient Current Technique (TPA-TCT) is a new characterization technique for semiconductor devices. It is based on the charge generation by a highly focused femtosecond pulsed laser beam in a very small voxel that can be positioned freely in the semiconductor. In contrast to other laser based TCT techniques a true 3D resolution is achieved.
The objective of the AIDAinnova project on TPA-TCT and the scope of this deliverable is to further develop the technology, enable other interested research groups to implement and fully exploit their own TPA-TCT systems and use the technique for cutting-edge detector technology evaluation. 

In this report we briefly revise the TCT method and its application and give a status on the present distribution of table-top TPA-TCT systems in the HEP detector community. We present a new laser that was developed in the framework of this project and is now commercially available. It is more compact, more robust and exhibits an improved stability in time in comparison to the previously employed laser. Furthermore, the light output can be obtained via an optical fibre. 

We also present a wide range of improvements and innovations in methodology and analyses methods around TPA-TCT. We introduce the Weighted Prompt Current (WPC) method, the mirror technique and the Single Photon Absorption (SPA) suppression technique for irradiated devices or for devices with crystal defects. Furthermore, we integrated the TPA-TCT charge generation mechanism into TCAD device simulations, and we explored the impact of temperature on the TPA-TCT charge generation. These techniques and findings are now available to the community for better exploitation of the TPA-TCT technology.

We promoted the TPA-TCT technique through our publications and presentations on workshops and conferences, but more importantly by offering to perform measurements on various devices for interested colleagues. Some examples are described in this document, covering irradiated sensors, LGADs and monolithic sensor types. To promote the technology and in order to train early-stage researchers on the technology we organized in cooperation with the CERN DRD3 collaboration a hands-on school on TCT measurements. 

Finally, we give an outlook for the technology and conclude that we have achieved the objectives set by the AIDAinnova project including the deliverable “Offer support towards the implementation of TPA-TCT systems and contribute to the evaluation of newly developed sensors technologies”.