Electrical, functional and performance characterization of silicon sensors is key in optimizing the design and developing innovating concepts. Through means of I-V and C-V measurements, generation currents, stability and power dissipation are evaluated. Such tests also consist the first step in the quality assessment of any silicon sensor production. Post-radiation (>1e15 neq/cm2) characterization at low temperatures (~-30oC) provides crucial information about induced defects, their different types (interstitials or displacements) as well as thermal runaway and operational stability. Through electrical probing of the guard rings, surface resistivity and edge effects are estimated, crucial to investigate breakdown modes and stability.
In a second stage, charged particle measurements provide an insight on detection efficiency and timing characteristics of the devices. Using multi-dimensional CFD analysis algorithms with variable re-fitting, the impact of doping distribution and field geometry on time resolution and induced signal shape can be evaluated. Through multi-temperature testing performance with respect to timing can be evaluated in the range of ~20psec for several technologies (LGADs, planar, 3D) before and after irradiation.
Introduction of Transient Current Techniques, either in single or two-photon implementation, more detailed study of the field, edge effects and spatial characteristics of the sensors can bee achieved. In sensor implementations with intrinsic gain (LGADs, APDs), such an approach combined with timing and charged particle measurements, allows of a detailed mapping of the gain layer and the understanding of acceptor removal effects, considered as the main source of post-irradiation gain reduction.
Towards achieving radiation tolerance up to fluences exceeding 1e17 neq/cm2, more in-depth characterization includes combination of Secondary Ion Mass Spectroscopy studies with all above mentioned technics. Combining advanced analysis technics with comprehensive characterisation and irradiation campaigns with respect to different implant species, sensor geometry and silicon technologies, results are obtained in a three axis approach: Defect engineering, Geometrical field optimization and Process optimization.