The Silicon Electron Multiplier: Concept and first Results

About

Silicon sensors for the next generation of collider physics experiments face increasingly demanding performance requirements, including spatial resolution below 10 µm, time resolution in the range of 20–50 ps, and radiation tolerance up to fluences of 10¹⁷ n_eq/cm². To address these challenges, a novel silicon sensor architecture has been developed: the Silicon Electron Multiplier (SiEM). In contrast to Low Gain Avalanche Detectors (LGADs) or Avalanche Photodiodes (APDs), where amplification is achieved through doped gain layers, the SiEM generates internal gain by applying an electric potential difference across a composite electrode structure embedded within the silicon bulk using MEMS fabrication techniques. Since the high-field region is shaped purely by geometry and applied voltages rather than by doping profiles, no gain-layer deactivation is expected from radiation damage, potentially allowing such structures to withstand fluences exceeding 10¹⁶ n_eq/cm². Simulations of the device using TCAD and Garfield++ Monte Carlo methods have demonstrated that gains in excess of 10 can be achieved through optimization of the multiplication electrode geometry and configuration. In this seminar, the SiEM concept is described along with the various fabrication routes pursued to produce functional demonstrators. The characterization of SiEM structures produced by Hamamatsu Photonics (HPK) is presented, including electrical measurements and test beam studies with minimum ionizing particles. These results are accompanied by simulations describing the expected device behaviour. First results from current-voltage characteristics of irradiated sensors are also reported. The measurements demonstrate that the amplification mechanism is indeed functioning as designed, and improvements to the SiEM configuration for future production runs are discussed.

Coffee will be served at 10:30