Speaker
Description
The acceptor removal mechanism is well established as a limiting factor for the operational lifespan of standard n-in-p Low-Gain Avalanche Diodes (LGADs) and has been extensively studied. However, with the emergence of new LGAD designs, such as resistive LGADs and compensated LGADs, attention must now shift to understanding donor removal at high initial donor concentrations ($>10^{16}$ atoms/cm$^3$). This mechanism has a significant impact on the performance of these next-generation detectors, which aim to meet the requirements of future high-energy physics experiments. In resistive LGADs, the donor-doped resistive layer enables high spatial resolution (a few micrometres), even with larger pixel sizes, while in compensated LGADs, potential frontrunners for 4D tracking at fluences exceeding $10^{17}$ 1 MeV $\text{n}_{\text{eq}}/\text{cm}^2$, the gain implant is achieved through a precisely balanced compensation of acceptor and donor doping.
In this contribution, we present a methodology for evaluating donor removal by observing changes in sheet resistance resulting from irradiation using van der Pauw test structures. Typically, these structures consist of the layer under study implanted in a substrate with opposite doping to minimise parasitic effects. However, we demonstrate that valuable insights can also be gained when the substrate shares the same doping type, thanks to comparisons with simulations. Furthermore, we show that donor removal can also be assessed through capacitance measurements in compensated LGADs when compared with simulations. The first results will be presented, highlighting the correlation between resistance- and capacitance-based methods and their potential as donor removal characterisation tools for next-generation LGADs.
