Spectroscopic ellipsometric measurements of the dielectric function of germanium dioxide films on crystal germanium

From spectroscopic ellipsometry measurements in the 1.5–5.7 eV photon energy range we determined the complex dielectric function of thermally grown germanium dioxide in the 1.0–6.3 eV range. A Kramers–Kronig consistent dispersion formula utilizing an exponential-shaped optical band edge was used in conjunction with both previously published far ultraviolet absorbance data for amorphous GeO2 and our spectra. These measurements show that ε2 for GeO2 can be regarded to be zero in the range of E<5.5 eV, which differs from a previous report. Using these new optical results for the investigation of oxide growth, we find that GeO2 grows via a parabolic growth law with a growth constant, kp=1.2×10−19 m2 s−1 at 550 °C.