Negative oxygen vacancies in HfO$_2$ as charge traps in high-k stacks

TL;DR

This paper investigates oxygen vacancies in HfO$_2$ and finds that negatively charged vacancies act as intrinsic electron traps, with calculated energies aligning with experimental electrical measurements, impacting high-k dielectric device performance.

Contribution

It provides first-principles calculations of oxygen vacancy energies in HfO$_2$, identifying negative vacancies as key charge traps in high-k stacks.

Findings

Thermal ionization energies match experimental data.

Negative oxygen vacancies are likely intrinsic electron traps.

Results inform defect management in hafnium-based devices.

Abstract

We calculated the optical excitation and thermal ionization energies of oxygen vacancies in m-HfO$_2$ using atomic basis sets, a non-local density functional and periodic supercell. The thermal ionization energies of negatively charged V$^-$ and V$^{2-}$ centres are consistent with values obtained by the electrical measurements. The results suggest that negative oxygen vacancies are the likely candidates for intrinsic electron traps in the hafnum-based gate stack devices.