First-principles study of transition-metal aluminates as high-<i>k</i> gate dielectrics

Abstract

The semiconductor industry is searching for a high-k gate dielectric replacement for silica. We study the electronic properties of Nb, Zr, Y, and Sc aluminates using density functional theory to screen aluminates for further study. The transition metals substituted favorably at the octahedral Al sites in the κ-alumina model system. Zirconium and niobium substitution for Al introduced localized d-electron states 0.6 and 1.1 eV below the conduction band. Yttrium and scandium introduced states 0.1 and 1.4 eV above the delocalized s and p states of the conduction band causing little change in the κ-alumina band gap and are promising replacement candidates that maintain the large alumina band offset.