Reconstruction of doping profiles in semiconductor materials using opticaltomography

A non-destructive and contactless method for doping profile characterisatio n in semiconductor materials is presented and analysed numerically in a one -dimensional geometry. It is based on the capability of optical diffraction tomography to reconstruct the complex refraction index of an object, illum inated at different wavelengths, starting from the measurements of scattere d field. Using a suitable model (Drude-Lorenz) to relate the complex refrac tive index of a semiconductor, at infrared wavelengths, to the carrier conc entration we establish a relation between the scattered field intensity and carrier concentration. The problem is treated as an inverse type and the s olution is defined as the global minimum of a proper functional. The effect iveness of this approach is demonstrated by simulating numerically the expe riment. (C) 1999 Elsevier Science Ltd. All rights reserved.