Effect of Ge passivation on interfacial properties of crystalline Gd2O3 thin films grown on Si substrates

Abstract

The incorporation of few monolayers of Ge chemisorbed on Si surface has been found to have significant impact on the electrical properties of crystalline Gd2O3 grown epitaxially on Si substrates. Although the Ge coverage on Si surface does not show any influence on the epitaxial quality of Gd2O3 layers, however, it exhibits a strong impact on their electrical properties. We show that by incorporating few monolayers of Ge at the interface between Gd2O3 and Si, the capacitance-voltage characteristics, fixed charge and density of interface traps of Pt/Gd2O3/Si capacitor are much superior to those layers grown on clean Si surfaces.

Epitaxial lanthanide oxide thin films on Si for high-k gate dielectric application: Growth optimization and defect passivation

“…Further increase of Ge coverage was reported to result in nonuniformity in C-V measurements across the wafer. 40 The estimated V FB in this case (10.3 V) indicates negligible amount Q f present at the interface. This improvement in the dielectric properties of the Gd 2 O 3 layers was found to be independent of the Si surface orientation.…”

“…11), which infers to a large number of intrinsic/extrinsic defects present at the interface. 39 Such instability occurs due to the accumulation of mostly positive fixed charges at the Gd 2 O 3 /Si interface created during C-V sweeping, 39,40 which could significantly degrade the electrical performance of any device. 41,42 Laha et al reported Q f ;9.5 Â 10 12 cm À2 for epitaxial Gd 2 O 3 on Si which is only two orders of magnitude lower than the atomic density of dangling bonds on a nonreconstructed Si(001) surface.…”

“…This implies that approximately 1% of Si surface bonds remain unsaturated even after oxide growth onto it. 40 Each Si surface atom possessing a dangling bond usually seeks an additional electron to become electrically neutral. They tend to capture the required electrons from the oxide layer near the interface, thereby creating large number electron vacancies, i.e., positive charges, which results in a large shift of the flat band voltage.…”

“…Laha et al investigated the influence of chemisorbed Ge layer on the growth and dielectric properties of epitaxial Gd 2 O 3 layers on Si. 40 In this approach different amount of Ge (0.15-3 ML) was deposited by e-beam evaporation on clean Si surfaces prior to the Gd 2 O 3 layer growth. The in situ RHEED patterns of the Gd 2 O 3 layers grown on such Ge-covered Si surfaces (Fig.…”

Enhanced Electrical Properties of Carbon Doped Epitaxial Gd2O3 Thin Films on Si Substrates

“…Figure 3 compares the capacitance-voltage (C-V) hysteresis of epitaxial Gd 2 O 3 layers grown under three different conditions on Si(001) substrates. The epi-Gd 2 O 3 layer prepared under optimum condition shows negligible hysteresis and flat band shift (8). It is interesting to see how important it is to maintain the sufficient oxygen supply during oxide layer growth.…”