Determination of minority-carrier lifetime and surface recombination velocity by optical-beam-induced-current measurements at different light wavelengths

An analysis of the optically generated excess current through a plane p-n junction perpendicular to the surface is given both for the steady state and for periodic generation. The finite dimensions of the sample are taken into account. The sample is assumed to be bounded by a plane parallel to the junction. An exponential light generation function according to Beer’s law is considered. By variation of the wavelength and thus the penetration depth of the light, the influence of surface recombination on the measured signal can be controlled. Therefore, the determination of bulk diffusion length and surface recombination velocity is unambiguously possible from a set of steady-state optical-beam-induced-current curves at different light wavelengths. From additional high-frequency measurements, the diffusion constant and thus the bulk lifetime of the excess carriers may be obtained. The results are demonstrated by measurements on various p+nn+diodes.