SIMULTANEOUS DETERMINATION OF THE COMPOSITIONS AND THICKNESSES OF A MULTILAYER FILM USING SPECTROREFLECTOMETRY

In the growth of III-V epitaxial layers, spectroreflectometry is a fas t, convenient method for measuring layer thickness. The experimentally measured optical thickness is the product of the composition-dependen t refractive index and the layer thickness. In the past, the thickness of a ternary layer was uniquely determined by fixing the composition using photoluminescence or x-ray measurements. In this article, we sho w that the decoupling can be accomplished by measuring and fitting the spectroreflectance in a wavelength range where there is significant v ariation of the refractive index, for example, near the semiconductor band gap. The technique is demonstrated by the simultaneous measuremen t of the compositions and thicknesses of multilayered AlGaAs/GaAs film s incorporating up to three different AlGaAs compositions. (C) 1998 Am erican Institute of Physics.