To determine the optimal interface between a-HfO2 igh-K oxide and Si0.5Ge0.5(001), density functional theory molecular dynamics (DFTMD) simulations of several amorphous stoichiometric and sub-stoichiometric SiOxNy interlayers were performed. The stack with oxygen deficient a-SiO interlayer demonstrated superior electric properties because it avoided all dangling bond formation. Experimental studies confirmed that a nearly pure SiOx interface between a-HfO2 and SiGe(001) could be formed which correlated with a low interface state density.