Low-frequency noise assessment of the silicon passivation of Ge pMOSFETs

The impact of the silicon passivation layer thickness on the low-frequency (LF) noise performance in linear operation of Ge pMOSFETs has been studied, for devices with different channel lengths. It is shown that for 8 monolayers (MLs) of Si, the LF noise is predominantly 1/f-like noise, which is governed by defect-assisted carrier number fluctuations for most of the device lengths studied. When going to thinner passivation layers, the noise mechanism and origin are changing, particularly in weak inversion and for long devices. The complexity of the LF noise performance is not completely understood yet, which is required in order to optimize the gate stack from a viewpoint of analog/mixed signal operation.