Quantitative approaches in laser scattering tomography

Abstract

Laser scattering tomography (LST) is extended to quantitative measurements and to macroscopic fields. A technique is described to image patterns of submicroscopic scatterers decorating defects in depths up to a few mm without focus degradation. It is especially useful to reveal the arrangement of precipitates of low concentration and assures the proportionality between the measured intensity of the scatterer and its scattering cross-section. The relative volumes of the submicroscopic precipitates are determined from the measured intensities. The extended LST technique is demonstrated for GaAs crystals grown by the vapour pressure controlled Czochralski (VCz) technique. Statistically relevant histograms of the volumes of submicroscopic As precipitates are presented. By Fourier analysis planes preferably populated by decorated dislocations can be evaluated for their orientation. Dependencies along macroscopic dimensions of the samples can be measured, e.g. along a wafer radius.