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〈 + i 〈ε2〈 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, E ′0, E2, and E ′2 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)