Effective surface passivation methodologies for high performance germanium metal oxide semiconductor field effect transistors

We demonstrate methodologies to improve the interface characteristics between a germanium (Ge) substrate and high-k gate dielectrics. GeON and SiOx were investigated as passivating layers on a Ge surface. Smaller hysteresis and interface state density (Dit) were obtained using SiOx interface layer and p-type metal oxide semiconductor field effect transistors (MOSFETs) fabricated with a gate stack of Ge/SiOx/HfSiO/WN showed about two times higher effective mobility compared to universal Si/SiO2 MOSFET. Because the formation of GeOx at the interface resulted in higher hysteresis and equivalent oxide thickness, the effective suppression of growth of unstable GeOx by SiOx interface layer contributed to the good device characteristics of the fabricated devices.