Reconstruction of doping profiles in semiconductor materials using optical tomography

A non-destructive and contactless method for doping profile characterisation 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, illuminated at different wavelengths, starting from the measurements of scattered field. Using a suitable model (Drude-Lorenz) to relate the complex refractive index of a semiconductor, at infrared wavelengths, to the carrier concentration we establish a relation between the scattered field intensity and carrier concentration. The problem is treated as an inverse type and the solution is defined as the global minimum of a proper functional. The effectiveness of this approach is demonstrated by simulating numerically the experiment. (C) 1999 Elsevier Science Ltd. All rights reserved.