Improvement of the electrical performance of Au/Ti/HfO 2 /Ge 0.9 Sn 0.1 p-MOS capacitors by using interfacial layers

Abstract : The impact of different interfacial layers (ILs) on the electrical performances of Au/Ti/HfO 2 /Ge 0.9 Sn 0.1 metal oxide semiconductor (MOS) capacitors is studied. Parallel angle resolved x-ray photoelectron spectroscopy measurements show that germanium diffuses into the HfO 2 layer when no IL is used. This results in an increase in the tin content at the interface and a high interface state density. We demonstrate that the use of an IL prevents germanium and HfO 2 intermixing and improves the electrical performance of MOS capacitors. Several ILs are studied such as alumina (Al 2 O 3) and plasma oxidized GeSn (GeSnO x) prior to HfO 2 deposition. C-V measurements correlated with simulations made by a customized analytical model indicate an interface state density of 5 Â 10 11 eV À1 cm À2 for the HfO 2 /GeSnO x /Ge 0.9 Sn 0.1 gate stack. This result is promising for the integration of high mobility GeSn channels in CMOS devices.