First principles study of defects in high-k HfO2

Intrinsic defects and doping N, Si, Al, and Ta defects in monoclinic HfO2 were investigated by using the first-principle calculations based on density functional theory (DFT). The results show that the defects of TaHf+1, AlHf−1, VHf−4 are stable under oxygen-rich conditions; while the Hfi+4, VO3+2, NO4−1 are stable when the conditions are hafnium-rich. It is revealed that the defects under hafnium-rich conditions are easy to form, and the results also show the properties of negative -U. Defects of the thermodynamic transition levels in the Si band gap can capture or release the charge. It will result in the effect of Fermi level pinning, so it can seriously affect the stability of the device.