The applicability and limits of time-resolved transillumination to determine the internal details of biological tissues are investigated by phantom experiments. By means of line scans across a sharp edge, the spatial resolution (Ax) and its dependence on the time-gate width (At) can be determined. Additionally, measurements of completely absorbing bead pairs embedded in a turbid medium demonstrate the physical resolution in a more realistic case. The benefit of time resolution is especially high for a turbid medium with a comparatively small reduced scattering coefficient of approximately pL,' = 0.12 mm-1 . Investigations with partially absorbing beads and filled plastic tubes demonstrate the high sensitivity of time-resolving techniques with respect to spatial variations in scattering or absorption coefficients that are due to the embedded disturber. In particular, it is shown that time gating is sensitive to variations in scattering coefficients.

Emission microscopy has now become established as an effective technique in terms of reliability physics of industrial semiconductors. This convenient method allows chip verification and failure analysis to be carried out in many applications. Besides this, emission microscopy provides a technique for use in device engineering and the optimization of test structures. The key to using this technique to permit a more sophisticated quantitative analysis lies in a unique assignment of the light emission to the defect mechanism. Since the corresponding phenomena are numerous and their details are not fully clarified in all cases, further investigation is still required before this technique can be used routinely in a quantitative rather than qualitative approach. Some quantitative aspects of emission microscopy with respect to fundamental studies will therefore be outlined in this article, and the applicability of such practical guidelines will be illustrated. This provides the fundamentals for a comprehensive evaluation of the potential applications and degree of informativeness of this advanced method of failure analysis.

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The fundamentals of light-emitting phenomena from silicon semiconducting material are presented from an experimental rather than a theoretical point of view. The following aspects are considered in detail. In the first place, laterally resolved measurements give information about the distribution of emitted light, which has been generated by an excited radiative system. Secondly, spectrally resolved experiments enable a distinction to be made between different current transport mechanisms and permit discussion of underlying physical concepts. Thirdly, some fundamental emission mechanisms are discussed on the basis of the dependency of the electroluminescence intensity on such external parameters as temperature and current. Finally, the applicability of these mechanisms with respect to reliability physics, design verification and failure.analysis of semiconducting'devices is outlined and the state of the art of emission microscopy is reviewed.

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