Simulation study of silicon photomultiplier with metal mesh on the surface

Silicon photomultiplier (SiPM) is a kind of array solid state photodetector which uses avalanche multiplication mechanism to detect weak light. It has very high detection sensitivity and is an excellent solution to the problem of weak light detection. Due to the thin thickness of the doped layer with high concentration impurity atoms on the surface of the existing SiPMs with bulk resistor quenching mode, the voltage of G-APD at different positions is not uniform. To solve this problem, SiPM with surface metal mesh structure is proposed in this paper, and the process and device simulation are carried out by Silvaco simulation software. The structure can improve the photon number resolution of SiPM by filling metal mesh holes on the surface of SiPM high concentration ion doping layer, so that the two ends of the G-APD cells in different regions have consistent bias. The process simulation results show that the growing oxide layer before ion implantation will affect the breakdown voltage of SiPM, and the breakdown voltage will increase with the increase of oxide layer thickness. The device simulation results show that the mesh structure improves the uniformity of electric field distribution among adjacent G-APD cells. In addition, the incident light can form multiple reflections between the metal mesh structure and the packaging medium, and a part of the light in the non-photosensitive region will be refracted into the photosensitive region. The simulated light response results show that the peak photocurrent is increased by 5% at room temperature when the over-voltage is 2.5 V.