Defect-Related Excess Low-Frequency Noise in Ge-on-Si pMOSFETs

The low-frequency noise in strained and relaxed Ge pMOSFETs is characterized to investigate more closely the anomalously large current spectral density at low drain currents. As shown, the dominant Lorentzian spectrum found in weak inversion points to fluctuations by generation-recombination (GR) events at substrate defects. This is confirmed by the fact that strained Ge transistors, having a significantly lower threading dislocation density, also exhibit lower excess GR noise. The usual number-fluctuation 1/f noise becomes more pronounced above threshold and also for shorter gate lengths.