Influence of Surface Resistance of Silicon p-i-n Photodiodes n+-Layer on their Electrical Parameters

Silicon quadrant p-i-n photodiodes of different concentrations of diffused phosphorus in the n+- layer were fabricated. The experimental curve of phosphorus impurity distribution along the depth of the diffusion layer is obtained. The influence of charge carrier concentration in this layer on the dark currents of responsive elements and the guard ring was studied. Volt-ampere characteristics of photodiodes were measured. It was seen that when the surface resistance of the n+-layer decreases, the dark currents decrease, the samples with a surface resistance of 1,9 – 2,4 Ohm / □ have approximately the same level of dark currents of responsive areas, i.e. further increase in charge carrier concentration makes no change. As to dark currents of photodiode guard rings, it was found that for the most part they depend on the state of the crystal periphery but not on the level of doping. The influence of the surface resistance of the n+-layer on  interconnection resistance between the responsive areas and the protective ring, and no influence on the capacitance of the photodiodes were revealed.