Electronic structures of transitional metal aluminates as high-k gate dielectrics: first principles study

The electronic structures like bandgap and density of states (DOS) of different transitional metal (Y, Sc, Zr, Hf and Ta) aluminates have been studied using density functional theory (DFT) and local density approximation (LDA). The transition metals are substituted favorably at the octahedral Al sites in the a-alumina system. The problem of a decreasing bandgap in Zr, Hf or Ta aluminates predicts the band offset reduction from the introduction of 4d or 5d states below the conduction band edge. While, in case of Y or Sc aluminates, there is no such decrease in the bandgap and it becomes more suitable for the device performances.