Characterization of defects in semiconductors by combined application of SEM(EBIC) and SDLTS*

Besides the characterization of the geometrical structure of defects in semiconductors by TEM the estimation of their electrical activity is of importance. SEM(EBIC) and SDLTS (scanning deep level transient spectroscopy) are especially suitable for this purpose; they allow the inspection of electronic properties with a spatial resolution in the micron-range. On the one hand, SEM(EBIC) yields information on the recombination efficiency of defects in the crystal volume adjacent to a pn junction or a Schottky barrier; on the other hand, SDLTS enables the detection to be carried out of the distribution and the energetic levels of deep level defects lying in the space charge region. Accordingly, the combined application of these techniques is very promising for investigating physical processes implying an inhomogeneous incorporation of deep level defects in semiconductor crystals. In comparison to the widely used SEM(EBIC) technique SDLTS has only rarely been applied, a fact that is due to the high detection sensitivity necessary for measuring capacity transients. The application of a highly sensitive (10^—6 pF) micro-computer-controlled SDLTS system in combination with a conventional EBIC system allows a reliable inspection of semiconductor materials and devices, based on A₃B₅ compounds and on silicon. A typical application of the above technique is the investigation of the impurity distribution around extended crystal defects, like dislocations and precipitates, to study their gettering activity.