Speaker
Description
The results from an innovative batch of Low-Gain Avalanche Diodes (LGADs) produced by the Fondazione Bruno Kessler (FBK, Italy) will be presented.
The sensors are p-in-n LGADs, where the high-concentration implant that generates charge-carrier multiplication is provided by an n-type dopant (nLGAD). The nLGADs are produced on thin epitaxial n-type substrates, with an active thickness of 55 $\mu$m. A completely new design for the p$^{++}$ ohmic contact and the n$^+$ gain implant has been developed, with careful consideration of dopant activation and diffusion during production. Furthermore, extensive R&D on peripheral structures optimised for n-type thin substrates has been incorporated into the batch, resulting in 10 guard ring designs. Fourteen wafers are produced with different diffusion and implant depths, using Boron on the p$^{++}$ contact and two different dopants, namely Phosphorus and Arsenic, for the n+ implant.
The NLGAD sensors will provide unique information on the donor-removal mechanism at a concentration of about 10$^{16}$ atoms/cm$^3$. This study will provide fundamental knowledge for the design of p+–n+ compensated LGADs on the path to extreme fluences. Moreover, nLGAD sensors are valuable tools for detecting low-energy photons.
Preliminary results on the sensor characterisation on the wafer and after dicing will be presented and discussed.