The SiGeC ternary alloy seems to be an attractive material system for Si-based device applications, because the incorporation of a small amount of C in the high-mobility SiGe layer offers an additional degree of freedom for tuning the bandgap, band offsets and the lattice strain in group IV heterostructures. In this work, detailed low-frequency noise (LFN) results in SiGeC pMOSFETs are presented. Our experimental results in saturation regime of the SiGe MOSFET show that the noise in SiGeC MOSFETs at gate bias |VGS-VT|<0.4V can be referred to the gate terminal as a noise voltage SVG=VG2, which implies (ΔN) fluctuation with correlated noise in the cap and SiGeC channel currents. Overall, the trend shows that the gate referred noise voltage scales inversely with the gate area, and that the variation of the noise level has log-normal distribution. Therefore, the noise in SiGeC MOSFETs can be expressed as S=Savg*exp(t*σNp), where t=±1,...,±3 is a coefficient selected for desired confidence probability of 0.6,...,0.99 respectively, and σ is the standard deviation of the log-normal distribution of the noise level around its average Savg, later given by (ΔN-Δμ) fluctuation in the cap layer and SiGeC channel of pMOSFET.
The low frequency noise (LFN) properties of the field-effect transistors (FETs) using polymers as the semiconducting material in thin-film transistor (TFT) structures are investigated and discussed in terms of the charge carrier transport. Results obtained from several research groups are summarized. Injection-drift limited model (IDLM) for charge transport in amorphous PFETs is discussed. IDLM has some advantages in comparison to the commonly used metal-oxide-semiconductor (MOS) transistor models. A general trend of proportionality between noise power density and the DC power applied to the polymer FET’s (PFET’s) channel is observed in the data from several research groups. This trend implies mobility fluctuation in PFET as the dominant noise source.
A physically-based transient microplasma based model for low frequency noise in pn diodes is discussed and implemented in SPICE simulator. The simulation indicates that the model correctly describes the non-monotonic behavior of both the DC and the noise characteristics of diode at the onset of avalanche breakdown. Since the model is based on a new microplasma switching theory, the results of simulation confirm the findings of this theory. These are, as follows for the microplasma. Its switching threshold is the condition of equality of free- to space charge concentration in depletion layer. Its on-current is approximately twice the threshold current. It is initialized by the charge generation due to few recombination centers in microplasma region at high avalanche multiplication due to impact ionization, while the microplasma turn-off is due to carrier diffusion from microplasma region into the depletion layer at low, but larger than 1, avalanche multiplication.