Oxygen vacancy related hole fast trapping in high mobility cubic-Ge/ZrO2 interface

Abstract

Ge has the potential to replace Si as the future field-effect transistors channel material due to its superior hole mobility, and cubic zirconia with high dielectric constant and small lattice mismatch can be selected as its oxide layer. At present, the mechanism of charge trapping caused by defects in the Ge oxide layer interface and bulk of such device has not been accurately analyzed. In our work, we have constructed the cubic Ge/ZrO2 interface, and studied the electronic structure and hole trapping characteristics of the interface structure by first-principles hybrid-functional calculations with Marcus theory. According to research oxygen vacancies with the different distances (abbr. d O-int) away from the Ge substrate, we confirm that the oxygen vacancy can act as a fast trap center to capture the hole of the valence band maximum (VBM) from Ge, resulting in the ultrafast or fast transient charge trapping in the high-k gate dielectric. We found that, when a given range of applied electric field, the hole trap is ultrafast with capture time of 10−6–10−5 when d O-int is within the range of 2–7 , and there is a 2–3 order of magnitude increases in capture time as d O-int exceeds 7 with the maximum capture cross section reducing substantially. Here, our work provides a clear and reasonable description of the distance-dependent hole trapping process at the Ge/high-k dielectrics metal-oxide-semiconductor (MOS) devices and provides significant support for solving the reliability problem of microelectronic devices.