Correlations between first-principles calculations and electric properties of HfO_2:Al_2O_3 alloys for metal-insulator-metal (MIM) capacitor applications

摘要

The electronic structure and optical properties of monoclinic HfO_2 (m-HfO_2) and HfO_2:Al_2O_3 alloys, from the density functional theory (DFT), are investigated. The calculated lattice parameters and optical properties of m-HfO_2 are consistent with the experimental data. Upon alloying with Al_2_3 (more than 25%), we observe that the bandgap of Hf-aluminate (HfAlO) increases. Moreover, some doping states in the top and bottom valence bands are induced, which enhance the visible absorption of HfO_2. From the impedance spectroscopy analysis, it is observed that 90% of the Al_2O_3 content in HfO_2 induces a reduction of oxygen vacancies (and ac conductivity) as well as an increase in the dielectric constant as compared to pure HfO_2. In addition, from the J-V and C-V variations, both current density and capacitance voltage nonlinearities are reduced. The conduction mechanisms of HfO_2 and HfAlO dielectrics are systematically investigated. According to the J-E plots, parameters like the optical dielectric constant and the effective barrier height are extracted. Results are consistent with the DFT calculations and show that the Hf_(0.1)Al_(0.9)O device may constitute a potential candidate for metal-insulator-metal capacitor applications.