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 mod el with temperature-and/or-composition-dependent coefficients, is presented . The model is further inverted by a simple algorithm to retrieve temperatu re and composition information from optical measurements obtained by spectr oscopic 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 be tween 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 algorith m with recursive "whitening" of the error, which shows fast convergence to a near-optimal solution, even when handling a large number of parameters. T he level of accuracy achieved makes this method an adequate sensor for temp erature, composition, and thickness control during molecular beam epitaxy g rowth. (C) 1999 American Vacuum Society. [S0734-211X(99)06403-3].