Optical properties of amorphous high-k LaGdO3 films and its band alignment with Si

Optical properties of pulsed laser ablated amorphous high-k LaGdO3 (LGO) thin films on quartz (0001) substrates and its conduction/valance band offset with Si were studied. Complex refractive index and bandgap were extracted from the transmission spectra. An increase in the bandgap with decreasing film thickness was observed. The degree of structural disorder frozen in the network was estimated using Urbach model and found that the amorphousness increased with decreasing thickness. The analysis of refractive index dispersion with wavelength confirmed the single-effective-oscillator model for the direct inter-band transition. The calculated conduction and valance band offset of LGO with silicon were 2.57 ± 0.15 eV and 1.91 ± 0.15 eV, respectively, and are high enough to suppress the electron or hole injection into the conduction and valence band of LGO from the Si substrate, hence, can be of use as new high-k dielectric for the Si based CMOS technology.