Study of La-Induced Flat Band Voltage Shift in Metal/HfLaOx/SiO2/Si Capacitors

The flat band voltage in metal/HfLaOx/SiO2/Si capacitors has been investigated as a function of La concentration in HfLaOx. We have found that with an increase of La concentration, the flat band voltage shifts to the negative direction. Furthermore, we demonstrate that the flat band voltage in this system is determined by the La concentration at HfLaOx/SiO2 interface. This result suggests that the flat band voltage shift is due to the dipole layer formed at the HfLaOx/SiO2 interface rather than the Fermi-level pinning at the metal/HfLaOx interface.