Low-frequency noise mechanisms in Si and pseudomorphic SiGe p-channel field-effect transistors

Abstract

Measurements of low frequency noise in Si and Si0.64Ge0.36 p-channel metal oxide semiconductor field effect transistors are compared with a model of carrier number fluctuations due to tunneling into an energy independent density of oxide trap states (Nox) and associated mobility fluctuations. The failure of the model to explain the data leads us to suggest that reduced noise in the SiGe device as compared to Si is primarily associated with an energy dependence of Nox and a displacement of the Fermi level at the SiO2 interface in the heterostructure relative to the Si control.

Low-Frequency Noise In Advanced Mos Devices

“…This has been reported for buried channel Si MOSFETs, 67,[78][79][80] SiGe pMOSFETs, 12,81 SOI four-gate transistors, 82 f completely since the mobility fluctuation noise still remains. However, is it possible that the mobility fluctuation noise is enhanced by the gate oxide interface as well?…”

“…However, by biasing the surface Si and buried SiGe channel pMOSFETs in an appropriate way so that the quasi-Fermi levels in the two devices are equally distant from the valence band edges, the extracted trap densities would be roughly equal. In a recent publication, 82 Prest and co-workers were successful with this kind of exercise by including a Hooge mobility fluctuation noise term (α H = 2×10 -5 ) also, which was not considered in earlier work.…”

“…Moreover, Prest et al could not explain their data using only correlated mobility fluctuations. 82 A third alternative to explain the lower 1/f noise in buried SiGe pMOSFETs is to invoke mobility fluctuations. The fact that Hooge mobility fluctuation noise often is found to be the dominant 1/f noise source in pMOSFETs was neglected in the previous models.…”

Low Frequency Noise in Insulated-Gate Strained-Si n-Channel Modulation Doped Field Effect Transistors

“…This dominant contribution of contact noise can be found in many publications for different FETs, 21,22) including p-SiGe MOSFETs. 10) However in the devices presented here, noise always decreases with increasing gate voltage overdrive (see Fig. 5) indicating negligible contribution of the contact noise.…”

“…6) Due to the relative immaturity of the s-Si technology, noise characterization of these devices is limited. The low frequency noise in p-type strained-SiGe MOSFETs has been studied in multiple papers [7][8][9][10][11][12][13][14] and references therein. However, noise studies in n-channel strained-Si modulation doped FETs (MODFETs) have been reported in a few publications only dealing with Schottky gate devices.…”