Characterization of novel trench-isolated LGADs for 4D tracking

In recent years, Low Gain Avalanche Detectors (LGADs) have shown the capability of timing measurements in the tens of ps range for minimum ionizing particles. However, the segmentation of LGADs creates regions with no gain and provides a hindrance in achieving 100% fill factor (FF) for many applications and using LGADs as 4-dimensional (4D) tracking devices. The new LGAD design based on the trench isolation technique (TI-LGAD) is very promising in reducing the no-gain region and hence increased FF which in turn makes them capable of 4D tracking. This paper describes the features of a new TI-LGAD sensors production by FBK, in which the no-gain region is reduced significantly by replacing Junction Termination Extension (JTE) and p-stop implant with slender trenches. A new R&D batch is produced in FBK within the RD50 collaboration, in which several border layouts and fabrication processes are implemented. The new TI-LGAD batch enables a systematic study to select the best fabrication process and border layout. In this paper, the electrical and laser characterization, isolation between pixels, and the results on the measurement of no-gain region between pixels are presented.