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 〈ε 〉 = 〈ε1〈 + iε2〈 of InAsx P1–x al-loy thin films from 1.5 to 6.0 eV at room temperature. The structures for the E1, E1 + Δ1, E0, E2, and E2 critical points (CPs) were observed in the data. We compare direct- and reciprocal-space methods of extracting CP energies Eg. 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. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)