Hole mobility characteristics under electrical stress for surface-channel germanium transistors with high-k gate stack

Abstract

This paper describes device degradation and mobility characteristics for germanium (Ge)-channel p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs) with HfO2 gate dielectrics. In order to understand the effect of trapped charges in high permittivity (high-kappa) gate dielectric and interface-trap states, we compare the hole mobility of the SiGe/SiO2/Si (SGOI) structure before and after applying an electrical stress. It is found that hot-carrier injection (HCI) and constant-voltage Fowler-Nordheim (F-N) stress cause mobility degradation in different mechanism. Even a negative-biased moderate F-N stress will give recovery of hole mobility. These results indicate that the device performance of a surface-channel SGOI device is easily affected by the specific trapped-charge state in high-kappa dielectrics and interface traps.