Improved Electrical Properties of Ge p-MOSFET With $ \hbox{HfO}_{2}$ Gate Dielectric by Using $\hbox{TaO}_{x} \hbox{N}_{y}$ 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 $ \hbox{HfO}_{2}/\hbox{TaO}_{x}\hbox{N}_{y}$ are investigated. Experimental results show that MOS devices exhibit much lower gate leakage current than MOS devices with only $ \hbox{HfO}_{2}$ 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 $\hbox{TaO}_{x}\hbox{N}_{y}$ on germanium surface prior to deposition of high-$k$ dielectrics can effectively suppress the growth of unstable $\hbox{GeO}_{x}$, thus reducing interface states and increasing carrier mobility in the inversion channel of Ge-based transistors.