The possibility of using proton implantation to correct the characteristics of silicon photodiodes

The measured electrical parameters of silicon pin photodiodes (PD) subjected to the implantation of defect forming ions and subsequent heat treatment are analyzed, which reveal a new way of reducing the dark current and enhancing the device yield. The data of the electrical measurements are compared with the results of the structural study. It was experimentally demonstrated that, to reduce the dark currents of silicon pin photodiodes with a guard ring (GR) based on diffusion planar n⁺-p junctions with a depth of ~3 μm, it is necessary to perform the local implantation of hydrogen ions with an energy of 100+200+300 keV at a dose of 2×10¹⁶ cm^-2 in the region between the main n⁺-p junctions and the GR with the capture of n⁺ regions. In addition, post-implantation annealing in vacuum at 300℃ for 2 h is needed. It was established that proton irradiation of the periphery of the planar n⁺-p junctions in this mode reduces their dark current due to the formation of a defect surface layer with compensated conductivity. Such a layer weakens the negative effect of the surface on the dark currents. Annealing of the irradiated structures at a temperature of 300℃ leads to the formation of a surface layer with a thickness of ~3 μm with a resistance optimal for the flowing of a part of the photosensitive area current to the GR. This layer is isolated from the bulk of the crystal by a buried layer with a thickness of 3-8 μm and the compensated conductivity, which only forms at the specified temperature. Thus, the experimentally determined mode of processing the periphery of a pin PD based on high- resistance silicon made it possible to improve the parameters of the finished photodiode structures and increase the device yield. (authors)