1f noise in GaAs MESFETS

An attempt was made to discriminate between number fluctuation and mobility fluctuation $\text{1}\text{f}$ noise in GaAs MESFETs. It was found, that both models could explain the data, even though the mobility fluctuation $\text{1}\text{f}$ model seems more likely.     

1/ƒ noise in diffused and ion-implanted MOS capacitors

Noise measurements in p-type diffused and ion-implanted MOS capacitors were conducted. It was found that there are three sources of $\text{1/?}$ noise: (1) number fluctuation $\text{1/?}$ noise. It is due to the interaction of holes with the surface oxide. (2) Bulk mobility fluctuation $\text{1/?}$ noise. It is due to the fluctuation in the bulk mobility. (3) Modulation $\text{1/?}$ noise. When inversion becomes important electrons in the inversion layer begin to interact with oxide traps. This gives rise to fluctuations in the surface potential, which in turn gives a $\text{1/?}$ modulation of the surface mobility or a direct modulation of the bulk resistance. The above experiment proves in a unique way that the two existing (1) and (2) models for the MOSFET can be observed simultaneously and lead to a surface potential fluctuating in a $\text{1/?}$ fashion.     

Comparison of two 1f noise models in MOSFETs

The noise expressions for the number fluctuation model and for the mobility fluctuation model of $\text{1}\text{f}$ in MOSFETs at low drain bias are derived and expressed in terms of the effective trap parameter [N_T(E_f)]_eff/? and in Hooge's parameter α_H, respectively. It is indicated how the turn-on voltage V_T of the device and the carrier mobility μ can be evaluated from the characteristics; the two parameters can then be determined from the measured drain noise. Both parameters have modest values; either model might be correct, but the present measurements cannot discriminate between the models. Silicon on sapphire MOSFETs have values for these parameters that are a factor 200 larger than other devices.     

New methods for carrier lifetime measurements in PπN structures

Usual lifetime measurements in $\text{P}{}^{\mathrm{+}}\text{πN}{}^{\mathrm{+}}$ structures determine a parameter which is sensitive to diffusion mechanisms under double injection conditions. This parameter is not characteristic of the recombination mechanism alone.We have proposed two new methods that are not very sensitive to diffusion mechanisms. As the experimental study shows, the measured parameter is the true recombination lifetime in the bulk.     

Nature of 1f frequency fluctuations in quartz crystal resonators

The frequency fluctations measured in quartz crystal resonators of quality factor Q are proportional to Q^?4.3. The quantum approach to $\text{1}\text{f}$ noise predicts fundamental fluctuations of the cross sections of elementary dissipative processes. Starting therefore from fluctuations of the total dissipative coefficient, a Q^?4-law is derived. Consequently, the noise is caused by dissipation fluctuations, rather than fluctuations in the density, or the real part of the Young modulus of the crystal.     

High-frequency 1ƒ noise of photocurrent and residual conductivity in CdS

Peculiarities of the photocurrent noise and of the residual (“frozen”) conductivity are analyzed theoretically for the model of a CdS-type photoconductor. The significant element of this model is the existence of the collective recombination barrier. It is shown that in the cases where such a model is realized, the appearance of $\text{1}\text{?}$ portions in photocurrent noise spectra as well as in the noise spectra of the residual conductivity should be expected. Experiments are proposed and carried out which confirm the existence of the connection between the occurence of $\text{1}\text{?}$ portions in the noise spectra and the presence of the collective recombination barriers. Thus, the nature of the high-frequency $\text{1}\text{?}$ portions which have been often observed in photocurrent noise spectra of CdS is established. These have been erroneously ascribed to peculiarities of exchange between the c-band and the traps. The direct experimental proof of the dominating role of the recombination barriers in the residual conductivity phenomena is obtained.     

Frequency dependence of C and ΔV/Δ(C−2) of Schottky barriers containing deep impurities

The frequency dependence of $\text{ΔV/Δ(C}{}^{\mathrm{?2}}\text{)}$ of Schottky barriers with deep impurities has been discussed on the basis of the depletion approximation. Systematic treatment has been developed of Schottky barriers having spatially distributed deep centers and useful expressions have been derived for $\text{ΔV/Δ(C}{}^{\mathrm{?2}}\text{)}$. It is shown that the impurity profile, the energy level and the electron emission rate of deep impurities can be determined by making measurements of the frequency dependence of $\text{ΔV/Δ(C}{}^{\mathrm{?2}}\text{)}$. The method of measuring $\text{ΔV/Δ(C}{}^{\mathrm{?2}}\text{)}$ has also been briefly described.     

Presence of mobility-fluctuation 1f noise identified in silicon P+NP transistors

The magnitude and location of mobility-fluctuation $\text{1}\text{f}$ noise sources have been identified by means of biasing a PNP transistor in a common emitter configuration with first a high and then a low source resistance. Comparison of the two noise spectra at the same base currents shows the low source resistor bias isolates the collector noise sources, and the high source rsolates base noise sources. The magnitude of the observed collector $\text{1}\text{f}$ noise gives an α ? 2 × 10^?6 from Kleinpenning's mobility-fluctuation theory. The base $\text{1}\text{f}$ noise gives an α ～- 10^?7 due to an impurity mobility reduction factor of about 100.     

1f, g-r and burst noise induced by emitter-edge dislocations in bipolar transistors

Noise measurements conducted on npn bipolar transistors have revealed that the emitter-edge dislocations give rise to both $\text{1}\text{f}\text{and}\text{g-r}$ noise, the resulting noise increasing with the number of dislocations. In dislocated devices, an $\text{α ? 1.8 × 10}{}^{\mathrm{?4}}$ has been found which accounts for the base 1/f noise as mobility-fluctuation noise. A 1/ff² burst noise spectrum was observed when dislocations are clustered.     

An analytical approximation for the Fermi-Dirac integral F32(η)

A simple analytical expression for the Fermi-Dirac integral of $\text{3}\text{2}\text{and}\text{1}\text{2}$ orders is proposed. This expression is valid for ? ∞ < η < ∞ with an error below 0.63% $\text{(j =}\text{3}\text{2}\text{)}\text{and}\text{0.53\% (j =}\text{1}\text{2}\text{)}$.