Floating field ring technique applied to enhance fill factor of silicon photomultiplier elementary cell

A silicon photomultiplier (SiPM) is a matrix of Geiger-mode avalanche photodiodes (GM-APDs) connected in parallel. One of the main drawback in the SiPm is the low Photon Detection Efficiency(PDE) also due to the low geometrical fill factor of the microcells array. This paper reports on the analysis and simulation of the single floating field ring technique, applied to the junction termination of the single cell of a Silicon Photomultiplier (SiPm). A floating guard ring is made along the border of the single microcell and it is not connected to the cathodic contact. Even if the ring is not electrically connected to the main junction, it mitigates the variation of the electrical field at the main termination. The effect of the junction-to-ring distance is analytically investigated by using cylindrical coordinates and an optimal distance together with the optimal width is found. Results show that the single floating ring reduces the junction edge electric field by keeping constant the size of the microcell allowing, then, an improvement for the geometrical fill factor. Results are supported by TCAD simulations.