Optical Dielectric Function Modeling and Electronic Band Lineup Estimation of Amorphous High-k LaGdO_3 Films

摘要

Optical constants of pulsed laser ablated amorphous high-k LaGdC>3 (a-LGO) thin films on quartz (0001) substrates were measured and analyzed. Refractive index (n ~ 2.05-2.29) and extinction coefficient (k ~ 0.004-0.017) were parameterized by analysis of the UV/Visible transmission spectra employing a Cauchy-Urbach dispersion model in the 300-750 nm spectral window and confirmed the applicability of this model in this wavelength region. The composition and chemistry of these dielectric films were studied by utilizing ATR-FTIR spectroscopy. The deduced pinning factor (S), 0.5 suggests that LGO/Si is an interacting interface. The parameter S was applied in the Cowley-Sze relation to estimate the interface trap density (D_(it)) to be 1.08 x 1013 states cm"2 eV~(-1). As grown LGO/p-Si heterojunction showed a downward Fermi-level (FL) pinning of 0.39 ± 0.02 eV. A complete Type I straddled band lineup of this gate dielectric/semiconductor heterostructure was determined by applying the charge neutrality level (CNL) model. The CNL of LGO was deduced to be 2.11 ± 0.05 eV above valence band maximum.