Microscopic control of SiGe/high-κ oxide gate stack for p-MOSFET hole qubits

The formation of GeOx and HfGeOx by-products, and the Ge diffusion at the interface between SiGe active layer and high-κ amorphous gate oxide (a-HfO2) are major issues that affect the mobility of SiGe channels in p-type metal–oxide–semiconductor field-effect transistors (MOSFETs). Experimental evidence suggests that the inclusion of multiple interlayers and Nitrogen incorporation may reduce these interface defects and prevent the formation of detrimental traps at the SiGe/oxide contacts. In this work, we address the problem by combining density functional theory and classical molecular dynamics simulations. Our results reveal that the introduction of an ultrathin a-SiO2/a-SiON bilayer between SiGe and a-HfO2 is an efficient solution to eliminate the mixed oxides formation, preventing the diffusion of germanium into the gate oxide and improving the p-MOSFET efficiency.