Low-frequency noise study of Ge p-MOSFETs with HfO2/Al2O3/GeOx gate stack

The low-frequency (LF) Noise of Ge planar pMOSFETs passivated with GeO_x interfacial layer, followed by a post-Al₂O₃-deposition plasma treatment and fabricated in Ge-on-Si substrates, was analysed in this study. While interface state density values comparable with mid-gap Si/SiO₂ can be achieved it is also important to study the density of border traps in the gate stack by LF noise. It is shown that for the Ge pMOSFETs predominantly 1/f^γ noise (γ ~1) has been observed. From an analysis of the dependence of the normalized drain current noise PSD or the input-referred voltage noise PSD (S_VG) it can be concluded that for not too high gate voltages number fluctuations (V_G~V_T) and correlated mobility fluctuations (V_G>V_T) are causing the flicker noise. From a plot of Svg¹/² versus I_D/g_m one can derive the density of border traps (N_bt) and the scattering coefficient (α_SC).