Bilayer gate dielectric of ZrO2 and Ho2O3 on 4H–SiC substrate: structural and electrical characterization

Abstract

This study focuses on the performance evaluation of the structural and electrical characterization with various gas concentrations of bilayer oxide gate dielectric ZrO₂ and Ho₂O₃ thin films on a 4H–SiC substrate. The structural characterization of XRD, FTIR, and XPS indicated the formation of Zr–O, Ho–O, Zr–O–Si, and Ho–O–Si bonds. The cross sections of oxide layers were examined through a high-resolution transmission electron microscope with a physical thickness of 4.77 to 5.53 nm. The absence of interfacial layers has been reasoned due to nitrogen atoms affect causing blockage of charge movement and oxygen diffusion between oxide layers and 4H–SiC substrate. It was observed that the ZrO₂/Ho₂O₃/SiC sample underwent oxidation with a gas concentration ratio of 90% O₂:10% N₂ has the highest energy band alignment of conduction band offset \(\Delta {E}_{v}\) ~ 3.18 eV and valence band offset \(\Delta {E}_{c}\) ~ 5.38 eV with highest electrical hard breakdown field of 9.7 MVcm⁻¹. The effective dielectric constant (\({k}_{eff}\)) ~ 33.54, effective oxide charge (\({Q}_{eff}\)), average interface trap density (\({D}_{it}\)), and slow-trap density have been obtained from the derivation of capacitance–voltage plot. The analysis supports the conclusion that the bilayer thin film oxidized with a gas concentration ratio of 90% O₂:10% N₂ produced the optimal electrical performance. This may serve as a high-k gate dielectric application in metal–oxide–semiconductor-based devices.