One of the key parameters determining detection properties of silicon PIN detector structures (p⁺-ν-n⁺ or n⁺-ν-p⁺) is minority carrier diffusion length in p-n junction regions p-n (p⁺-ν or n⁺-ν). The parameter concerned strongly depends on quality of the starting material and technological processes conducted and has a significant impact on detector parameters, in particular dark current intensity. Thus, the parameter must be determined in order to optimise the design and technology of detectors.

The paper presents a method for measuring the spatial distribution of effective carrier diffusion length in silicon detector structures, based on the measurement of photoelectric current of a non-polarised structure illuminated (spot diameter of 250 μm) with monochromatic radiation of two wavelengths λ₁ = 500 nm (silicon penetration depth of around 0.9 μm) and λ₂ = 900 nm (silicon penetration depth of around 33 μm). The value of diffusion length was determined by analysing the spatial distribution of optical carrier generation and values of photoelectric currents.