Surface and bulk leakage current in Trench-Isolated LGADs: implications for self-induced ghost signal

Abstract The research presented in this paper addresses several advanced and interconnected concepts in silicon detector physics, particularly bulk type inversion, guard ring (GR) leakage, and the distinction between surface and bulk leakage currents in the presence of defects and isolation structures but in absence of edge field termination structure (JTE). By studying the leakage current behavior, we explored the mechanisms behind self-induced signals, referred to as ghosts, in Trench-Isolated Low Gain Avalanche Diodes (Ti-LGADs). These ghost signals are enhanced when the innermost guard ring is left floating but are suppressed (or reduced below detectable levels) when the GR is biased to the same potential as the readout pad. This observation motivated a more systematic investigation of leakage current, aiming to disentangle the residual leakage contributions from the pad leakage in both irradiated and non-irradiated Ti-LGADs, fabricated within the RD50 and AIDAInnova productions at FBK, Trento. Our findings contribute to the ongoing R&D of radiation-tolerant Ti-LGADs for 4D tracking applications in future accelerator experiments.