Temperature-composition determination based on modeling of optical constants of III-V compound semiconductors measured by spectroscopic ellipsometry

A general procedure to fit optical constants, using a transfer function model with temperature-and/or-composition-dependent coefficients, is presented. The model is further inverted by a simple algorithm to retrieve temperature and composition information from optical measurements obtained by spectroscopic ellipsometry. The method was applied to fit: (1) the complex index of refraction of the system AlXGa1-xAs at 600 degrees C, for values of X between 0 and 1. (2) Two data bases of complex dielectric constants, for near-lattice-matched InGaAs and InAlAs, and around temperatures of 500 degrees C. The parameters of the model are determined with a least squares algorithm with recursive "whitening" of the error, which shows fast convergence to a near-optimal solution, even when handling a large number of parameters. The level of accuracy achieved makes this method an adequate sensor for temperature, composition, and thickness control during molecular beam epitaxy growth. (C) 1999 American Vacuum Society. [S0734-211X(99)06403-3].