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Direct measurement of surface recombination velocity has been achieved for n-InP, p-InP, and n-GaAs by a novel technique which is based on picosecond optical resolution of a transient diffraction grating, formed by an excess electron-hole plasma near the surface of the semiconductor. The influence of diffusion, bulk recombination, and surface recombination on the carrier density are included in the analysis of the experiment, which shows that the method is specifically sensitive to surface recombination velocity. Effects of the plasma density on the diffusion coefficient and the carrier lifetime are discussed.

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The theory of self-diffraction of light by transient free-carrier gratings in semiconductors has been expanded to the case in which nonlinear absorption of light creates the grating. Its application to the experiments performed allowed determination of the free-carrier ambipolar diffusion coefficients in CdS, CdSe, and ZnSe crystals, and the mechanism of free-carrier recombination and carrier lifetime in CdS at low temperatures.