Modeling of optical constants of InGaAs and InAlAs measured by spectroscopic ellipsometry

Two databases of complex dielectric constants, for InGaAs and InAlAs, near-lattice matched to InP, and around temperatures of 500 °C, have been fit using a transfer function model with temperature and composition-dependent coefficients. 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 model can be inverted by a simple algorithm to retrieve temperature and composition information from optical measurements obtained by spectroscopic ellipsometry. The level of accuracy achieved makes this method adequate for temperature, composition, and thickness determination during MBE growth.