Low-Gain Avalanche Detectors (LGAD) have gained high consideration in the past years thanks to proprieties such as time resolution below 30 ps. The first large-scale use of LGADs will be in the High-Luminosity LHC upgrades of CMS and ATLAS. LGAD are thin silicon sensors with internal gain supplied by a thin layer of highly concentrated Boron close to the junction. During neutron and proton irradiation, the Boron concentration is reduced by the acceptor removal process, thought to involve the creation of a neutral complex of Boron with the interstitial states in the silicon. This process leads to a reduction of the gain with fluence.
We have investigated the acceptor removal through neutron irradiation up to a fluence of 3E15 neq/cm2 by observing simultaneously a) the reduction in gain with charge collection studies with β-particles and b) the change in the bias voltage required to deplete the gain layer VGL using C-V measurements. We find perfect correlation between these parameters, although the correlations differ widely between LGAD produced by different manufacturers using different methods to extend the fluence reach of their LGAD. We will compare the acceptor removal of LGADs with Boron implanted at different depth and with additional Carbon implants.
|Submission declaration||Original and unpublished|