Dielectric properties of InAsP alloy thin films and evaluation of direct- and reciprocal-space methods of determining critical-point parameters

Spectroscopic ellipsometry is used to determine pseudodielectric function spectra = < + i < of InAsxP1-x al-loy thin films from 1.5 to 6.0 eV at room temperature. The structures for the E-1, E-1 +Delta(1), E-0', E-2, and E-2' critical points (CPs) were observed in the data. We compare direct- and reciprocal-space methods of extracting CP energies E-g. The direct-space values show less uncertainty, a result of how the two procedures use available information. Energies obtained are compared with the results of theoretical calculations using the linear augmented Slater-type orbital (LASTO) method. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.