Speaker
Description
Doping removal is one of the key radiation-damage mechanisms affecting the performance of Low Gain Avalanche Diodes (LGADs). In standard p-type LGADs, the degradation of the gain implant motivated detailed studies of acceptor removal at high initial doping concentrations, of the order of $10^{16}$ $\text{cm}^{-3}$. More recently, the development of new LGAD architectures, such as resistive LGADs, compensated LGADs and NLGADs, has extended this interest to donor removal as well.
A new methodology for the characterisation of radiation-induced doping removal was recently introduced, based on the measurement of sheet resistance variations after irradiation using van der Pauw test structures. This approach was first applied to both acceptor and donor implants with very high peak concentrations, around $10^{19}$ $\text{cm}^{-3}$, located at the Si–SiO$_2$ interface, namely the implants used to form the collection electrodes. The method was validated through a comparison between sheet resistance measurements and TCAD simulations based on SIMS-calibrated doping profiles. That study showed that, for this class of surface implants, donor removal proceeds approximately twice as fast as acceptor removal.
In this contribution, the same methodology is applied to buried acceptor and donor implants with peak concentrations around $10^{16}$ $\text{cm}^{-3}$, representative of the gain implants used in LGAD devices. These measurements will provide new initial-concentration points for the comparison between acceptor and donor removal. In addition, the new FBK NLGAD batch includes n-type gain implants based on both phosphorus and arsenic, allowing the role of different donor species in the removal process to be investigated.
| Type of presentation (in-person/online) | In-person presentation |
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