Germanium diffusion during HfO2 growth on Ge by molecular beam epitaxy

The authors study the Ge diffusion during HfO2 growth by molecular beam epitaxy on differently in situ prepared germanium substrates and at different growth temperatures. While HfO2 layers grown directly on Ge do not show any germanium contamination, oxygen rich interfacial layers such as GeOx or GeOxNy partly dissolve into the HfO2 layer, giving rise to high Ge contamination (from 1% to 10%). The use of nitridated interfacial layers does not prevent Ge diffusion into the HfO2 during the growth process because of the high oxygen content present in the nitridated germanium layer.