La2Hf2O7 high-k gate dielectric grown directly on Si (001) by molecular-beam epitaxy

We show that at deposition temperature in the 750-770 °C range, the La2Hf2O7 (LHO) compound can be grown crystalline on Sis001d. The predominant orientation is s001dLHO/ /s001dSi and f110gLHO/ /f110gSi and results in ultimately clean interfaces, indicating a strong tendency for cube-on-cube epitaxy. The ordered pyrochlore and random fluorite phases coexist in the dielectric. Acceptable gate leakage current, negligible hysteresis and high dielectric permittivity k,23 were obtained from electrical characterization of metal-insulator-semiconductor capacitors. The quality of interfaces and the good electrical characteristics make crystalline LHO a promising high-k candidate for the replacement of SiO2 in the gate of future aggressively scaled transistors.