High-κ dielectric gate stacks comprising HfO2 were fabricated on Ge with alumina as the barrier level. This was achieved by thermal annealing in an ultra high vacuum to remove the native oxide followed by deposition of aluminium by molecular beam epitaxy. After in situ oxidation at ambient temperature, HfO2 was deposited by atomic layer deposition. The devices underwent physical and electrical characterisation and show low EOT down to 1.3nm, low leakage current of less than 10−7 Acm−2 at ±1V, and CV hysteresis of ∼10mV. 
Low EOT GeO2/Al2O3/HfO2 on Ge substrate using ultrathin Al deposition