Improved AC conductance and Gray-Brown methods to characterize fast and slow traps in Ge metal–oxide–semiconductor capacitors

Abstract

We use an improved AC conductance method and a modified Gray-Brown method to study fast interface traps and slow border traps in Ge-based MOS capacitors. The combined methods provide the corrected Fermi energy level (E) versus gate voltage (V-g) relationship, even in samples with high densities of traps that cause significant C-V distortion, the energy distribution of interface traps, their capture cross sections (sigma), as well as slow border traps. A wide range of sigma's in p-type Ge is found, indicating that there is more than one type of interface trap near the Ge valence band edge. In contrast, a constant sigma near the Ge conduction band edge is observed in n-type Ge. XPS results indicate that Ge suboxides near the interface are accountable for the detected slow border traps. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691898]