The influence of the structure of guard rings on the dark currents of silicon p-i-n photodiodes

Abstract

The article examines the influence of the guard rings (GR) system structure on the dark currents of responsive elements (RE) and the actual guard rings of silicon 4-element p-i-n photodiodes (PD). The samples were made on the basis of p-silicon by planar technology. Samples with one, two, and three GR were produced. It was found that increasing the amount of n+-GRs does not reduce the dark current of the REs. But with an increase in the number of n+-GRs, the probability of an edge breakdown of the n+-p-junction in the regions of the exit of the hetero-junction of the GR to the surface increases. It is possible to reduce the levels of dark current of REs and GR by combining n+- and p+- guard regions, where p+-GR is a region of restriction of dark current leakage channels, isotypic with the substrate material. PD was made with p+-GR on the periphery of the crystal in the form of a concentric ring, as well as with a p+- region on the entire periphery of the crystal. This makes it possible to reduce the level of of dark current of n+- GR due to the reduction of the area of collection of charge carriers from the surface. But a significant decrease in the dark current of REs was not observed in such cases. We proposed to carry out boron diffusion in the gaps between REs and between REs and n+-GR.