Low-frequency noise in strained and relaxed Ge pMOSFETs

The low-frequency (LF) noise behaviour of pMOSFETs fabricated in strained Ge (sGe) and reference thick Ge-on-Si epitaxial layers has been compared. As is shown, the LF noise in the subthreshold regime is higher for the reference devices compared with the sGe, while in strong inversion, similar noise levels are achieved. The better noise performance in weak inversion is related to the lower density of threading dislocations in the sGe layers, leading to a lower drain-to-bulk leakage current. It is also demonstrated that in the low drain current regime, the noise spectrum is Lorentzian and independent on the gate bias, emphasizing the role of substrate defects in generating the LF noise fluctuations.