Gate Noise Research Articles

1/f noise in n-channel silicon-gate MOS transistors

It is found that equivalent gate noise power for l/f noise in n-channel silicon-gate MOS transistors at near zero drain voltage at room temperature is empirically described by two noise terms, which vary as K_{1}(q/C_{ox}) (V_{G} -V_{T})/f and K_{2}(q/C_{ox})^{2}/f, where V_{G} is gate voltage, V T is threshold Voltage, and C ox is gate-oxide capacitance per unit area. Unification of carrier-density fluctuation (McWhorter's model)and mobility fluctuation (Hooge's model) can account for the experimental data. The comparison between the theory and experiment shows that the carrier fluctuation term K 2 is proportional to oxide-trap density at Fermi-level. The mobility fluctuation term K 1 is correlated to K 2 , being proportional to \radic K_{2} . The origin of this correlation is yet to be clarified.

A discrepancy in the elementary theory of MOSFET modeling

The elementary theories of flicker noise in MOSFET’s operating at low drain bias evaluate the spectrum SVeq8f) of the equivalent gate noise emf δVeq under the assumptions of an effective mobility μeff that is independent of the gate voltage Vg and of a carrier number in the channel that varies linearly with the gate voltage. We show here that this introduces an error I2d/[g2m(Vg—VT)2] in the calculated results. Experiments show that this error can be significant, so that it makes some existing interpretations of SVeq(f) doubtful. The error comes about because at a given drain current Id the transconductance gm for large Vg−VT is smaller than the elementary theory predicts. This affects most MOSFET modeling at low drain bias.

Noise in triode-like JFET's

Drain noise measurements on the triode-like JFET show that the limiting noise of this device is thermal noise. We find <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{eq} = (2kT/q) \alpha g_{m}</tex> , where α is less than 2, which is smaller than in a vacuum triode. This device is, therefore, a low-noise device. The gate noise and the correlation susceptance were also measured. A theoretical analysis was carried out with a one-dimensional SCL current. The measured results agreed reasonably well with the theory. A two-dimensional analysis should be carried out in detail.

New estimate of the minimum noise figure of a m.e.s.f.e.t.

New estimates of the drain and gate noise multiplication parameters, the correlation coefficient and the minimum noise figure for a m.e.s.f.e.t. are advanced. For an uncooled GaAs m.e.s.f.e.t. having a 1 μm gate length, a minimum possible noise figure of 1 dB at 10 GHz is predicted. InP is only marginally better.

Correlation coefficient of gate and drain noise at high electric field

Correlation coefficient of gate and drain noise at high electric field

Measuring the spectral density of the gate noise current in field-effect transistors with a p-n junction

Measuring the spectral density of the gate noise current in field-effect transistors with a p-n junction

The Effect of Radiation Damage on the Noise Performance of Fet's

The gate noise from radiation induced defects in MOSFET's and JFET's has been studied for 24.8 MeV electron irradiations up to about 1 x 1016 e/cm2. The flicker noise increase induced in JFET's has been interpreted as due to the defect generation and recombination centers induced by radiation damage within the depletion layer. Finally, it is shown that the noise performance of JFET's is well applicable for high-intensity and high-level radiation detection.

Correlation coefficient of gate and drain flicker noise

Correlation coefficient of gate and drain flicker noise

Equivalent noise generators in JG FET

Van der Ziel has shown that at high frequencies the gate noise of a field effect transistor increases rapidly with increasing frequency. This effect is attributed to the thermal noise of the conducting channel and is caused by the capacitive coupling between the channel and the gate. Experimentally this effect can be shown to be negligible up to 3 MHz for n-type FET's 2 N 3966 where the cut off frequency is about 100 MHz. Experimental variation of the input noise current generator of the FET is then deduced.

FET noise sources and their effects on amplifier performance at low frequencies

In this brief review paper analytical results concerning the low-frequency (LF) amplifier noise performance of FET's are presented. The effects of interaction between the device basic noise sources, the small-signal model parameters, and the signal source admittance parameters are clearly indicated. The noise performance is found to be essentially determined by the effective surface-state density and the gate insulator thickness product ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N_{ss}t_{ox}</tex> ) in the case of MOSFET's, whereas in the case of JFET's, this is determined by the bulk density of impurity and/or defect generation-recombination (g-r) centers within the depletion region and the half-channel height squared product ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N_{TT}a^{2}</tex> ). Although an increase in the gate electrode area can reduce the equivalent gate noise resistance, this does not improve the noise performance of the device. Quantitative results based on typical device parameters are graphically presented with proper indications as to the upper limit of the LF range, the excess minimum noise figure, and the frequency range within which the noise figure remains below 3 dB level for specified source resistance values. The effects of gate leakage current on the noise performance of JFET's are included in these results.

Gate flicker noise in MOSFET's

A simple technique for measuring the gate flicker noise component in MOS field-effect transistors (MOSFET's) is presented. The method gives an estimate of the ratio of gate to drain flicker noise currents as compared to the ratio for thermal noise. In addition, the degree of correlation between the gate and drain flicker noise components can be obtained.

Induced gate noise in MOS FET's

Input admittance, drain noise and induced gate noise measurements are reported on several MOS FET's of large geometry. A few units show excess gate noise as found earlier by Halladay and van der Ziel. Other units show the gate noise expected from the thermal noise of the channel. No evidence was found of induced flicker gate noise even in noisy units that showed flicker drain noise up to 30 MHz. Rao and van der Ziel have shown theoretically that Christensson, et al's flicker noise models should give clearly observable flicker gate noise if a noticeable amount of flicker drain noise is present. Since none was observed, this indicates that these models may not be correct. Experiments seem to indicate that the h.f. input conductance g 11 varies as ƒ 3 2 in MOS-units with gate overlap whereas g 11 varies as ƒ 2 in MOS-units with no gate overlap. There is at present no satisfactory explanation for this difference; an ƒ 2 frequency dependence is expected theoretically.

Gate noise in MOS FET's at moderately high frequencies : J. W. Haslett and F. N. Trofimenkoff, Solid-St. Electron.14 (1971), p. 239

Gate noise in MOS FET's at moderately high frequencies : J. W. Haslett and F. N. Trofimenkoff, Solid-St. Electron.14 (1971), p. 239

Gate noise in MOS fet's at moderately high frequencies

A lumped model approach is used to evaluate the drain noise, gate noise and correlation between gate and drain noise for an n-channel enhancement MOS field-effect transistor. Effects of the substrate resistivity are examined in detail. It is found that as the substrate doping increases, the correlation coefficient increases over the value of 0·395 for an intrinsic substrate. This conclusion is in direct disagreement with previously published results.

The effect of the substrate upon the gate and drain noise parameters of MOSFETS : P. S. Rao, Solid-St. Electron.12 (1969), p. 549

The effect of the substrate upon the gate and drain noise parameters of MOSFETS : P. S. Rao, Solid-St. Electron.12 (1969), p. 549

On the gate current and noise behavior in pinched-off silicon junction field-effect transistors

An exponential relation between the gate current of the silicon junction FET and the drain applied voltage is obtained experimentally. It is found that the noise enhancement and input impedance decrease of this device starts at a point corresponding to the appearance of the gate floating potential which is related to the gate current.

Noise in solid-state devices and lasers

A survey is given of the most important noise problems in solid-state devices. Section II discusses shot noise in metal-semiconductor diodes, p-n junctions, and transistors at low injection; noise due to recombination and generation in the junction space-charge region; high-level injection effects; noise in photodiodes, avalanche diodes, and diode particle detectors, and shot noise in the leakage currents in field-effect transistors (FETs). Section III discusses thermal noise and induced gate noise in FETs; generation-recombination noise in FETs and transistors at low temperatures; noise due to recombination centers in the space-charge region(s) of FETs, and noise in space-charge-limited solid-state diodes. Section IV attempts to give a unified account of 1/f noise in solid-state devices in terms of the fluctuating occupancy of traps in the surface oxide; discusses the kinetics of these traps; applies this to flicker noise in junction diodes, transistors, and FETs, and briefly discusses flicker noise in Gunn diodes and burst noise in junction diodes and transistors. Section V discusses shot noise in the light emission of luminescent diodes and lasers, and noise in optical heterodyning. Section VI discusses circuit applications. It deals with the noise figure of negative conductance amplifiers (tunnel diodes and parametric amplifiers), and of FET, transistor, and mixer circuits. In the latter discussion capacitive up-converters, and diode, FET, and transistor mixers are dealt with.

The effect of the substrate upon the gate and drain noise parameters of MOSFETs

The effect of the substrate on the gate and drain noise parameters in MOSFETs is calculated up to first order terms in jw, under the assumption that the channel has thermal noise. It is shown that the substrate doping has little influence on the gate noise, i g 2 , and on the cross correlation between gate and drain noise i gi d ∗ . The theory cannot explain Halladay and van der Ziel's data. Therefore a non-thermal noise source must be operating in the channel.

On the high frequency excess noise and equivalent circuit representation of the MOS-FET with n-type channel

The noise in MOS-FET's is here represented by four parameters: the equivalent noise resistance R n (measuring the drain noise), the equivalent noise conductance g n (measuring the uncorrelated part of the gate noise) and the correlation admittance Y z = g z j ωC z (measuring the correlated part of the gate noise). For some large geometry units we compared the experimental values of these parameters with the ones calculated under the assumption that the noise in the channel was thermal noise. Serious discrepancies between the theoretical and the experimental values were noted, indicating that white noise of non-thermal origin must be present in the channel. The observed data are explained with the help of local “mobility fluctuations” in the channel. By making reasonable assumptions about this noise source, the observed data can be explained in a qualitative manner.

Theory and experiments of low-frequency generation-recombination noise in MOS transistors

A theoretical model for the generation-recombination (g-r) noise in MOS transistors is presented. This model takes into account the charge induced on all electrodes by the charge fluctuation of the impurity center in the depletion region. The model gives a finite equivalent gate noise resistance at saturation. Gold-doped and no-gold control devices were fabricated to verify the theory experimentally. The drain-voltage dependence of the g-r noise, which is shown to be distinctly different from the 1/f noise and thermal noise, is used to check the theory. Good agreement between theory and experiment is obtained.