The properties of six kinds of intrinsic point defects in monolayer GeS are systematically investigated using the “transfer to real state” model, based on density functional theory. We find that Ge vacancy is the dominant intrinsic acceptor defect, due to its shallow acceptor transition energy level and lowest formation energy, which is primarily responsible for the intrinsic p-type conductivity of monolayer GeS, and effectively explains the native p-type conductivity of GeS observed in experiment. The shallow acceptor transition level derives from the local structural distortion induced by Coulomb repulsion between the charged vacancy center and its surrounding anions. Furthermore, with respect to growth conditions, Ge vacancies will be compensated by fewer n-type intrinsic defects under Ge-poor growth conditions. Our results have established the physical origin of the intrinsic p-type conductivity in monolayer GeS, as well as expanding the understanding of defect properties in low-dimensional semiconductor materials.

Tetragonal ZrO2 high-k material as the dielectric layer of dynamic random access memory (DRAM) capacitors faces bulk defect related leakage current, which is one of the main obstacles to the down-scaling of DRAM devices. Boron and hydrogen impurities are known to be responsible for leakage current degradation and are hard to be removed in DRAM capacitors. However, the defect origins of boron and hydrogen leakage current are still puzzling, and corresponding suppression methods are urged. In this work, the properties of boron and hydrogen impurities in tetragonal ZrO2 are investigated using first-principles calculations, and defect types such as boron and hydrogen interstitials are discovered to have detrimental defect levels related to leakage current. Based on the discovery, a chlorine co-doping approach that can passivate detrimental defects by forming defect complexes is further proposed. By introducing level repulsion due to coupling between defect states, defect levels of passivated defect complexes are moved out of the region of leakage current contribution. Thus, bulk defect related leakage current in tetragonal ZrO2 based DRAM capacitors can be effectively suppressed without device structure modification, and a broad vista is opened for next-generation DRAM devices.

Ge has the potential to replace Si as the future FETs (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. dO-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 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 μs when dO-int is within the range of 2-7 Å, and there is a 2~3 order of magnitude increases in capture time as dO-int exceeds 7 Å 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 MOS devices and provides significant support for solving the reliability problem of microelectronic devices.

Hf1−x Zr x O2 alloy is recently employed as gate dielectric in complementary metal–oxide semiconductor (CMOS) devices because of its relatively low carrier trapping ability, low threshold voltage shift, and good reliability. Experimentally it is found that as the Zr concentration x increases, the device reliability caused by the defect‐related electron trapping would be improved. However, the trap nature in Hf1−x Zr x O2 alloy is still not yet well understood. Herein, using first‐principles hybrid‐functional calculations, the transition energies of some possible defects tending to occur in the experimental process for Hf1−x Zr x O2 alloys are discussed. The results show that, differing from previous studies suggesting that the oxygen vacancy (VO) is the main defect of electron trapping, the hydrogen interstitial (Hi), which can successfully explain the experimental observations of a reduction of the electron trapping ability as the Zr concentration increases, is more likely to be the origin responsible for the electron trapping in Hf1−x Zr x O2 dielectric. This work, therefore, broadens the understanding of electron trapping effect in high‐k dielectrics and gives guidance on improving the reliability in microelectronics.