Improved Electrical Properties of Ge p-MOSFET With HfO2 Gate Dielectric by Using TaOxNy Interlayer

The electrical characteristics of germanium p-metal– oxide–semiconductor (p-MOS) capacitor and p-MOS field-effect transistor (FET) with a stack gate dielectric of HfO2/TaOxNy are investigated. Experimental results show that MOS devices exhibit much lower gate leakage current than MOS devices with only HfO2 as gate dielectric, good interface properties, good transistor characteristics, and about 1.7-fold hole-mobility enhancement as compared with conventional Si p-MOSFETs. These demonstrate that forming an ultrathin passivation layer of TaOxNy on germanium surface prior to deposition of high-k dielectrics can effectively suppress the growth of unstable GeOx , thus reducing interface states and increasing carrier mobility in the inversion channel of Ge-based transistors.