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

• SiON inhibits the diffusion of Ge into HfO 2 and the formation of GeO x and HfGeO x . • The inclusion of amorphous SiO 2 /SiON improves the electrical quality of SiGe-HfO 2 . • Amorphous SiON saturates the SiO X dangling bonds at the interface. • Type-I band alignment between SiGe and HfO 2 . The formation of GeO x and HfGeO x by-products, and the Ge diffusion at the interface between SiGe active layer and high- κ amorphous gate oxide (a-HfO 2 ) 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-SiO 2 /a-SiON bilayer between SiGe and a-HfO 2 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.