X.C. Zhu

A theory of the Hooge parameters of solid-state devices

Handels theory of quantum 1/f noise is applied to the Hooge parameters of bipolar transistors and various types of FETs. Very low values for the Hooge parameters α Hn and α Hp for electrons and holes are obtained. For several cases the experimental data seem to agree with the predicted theoretical limit whereas in other cases the mobility 1/f noise is masked by other noise sources. In good GaAs devices the predicted quantum limit for α Hn is reached within a factor 5-10. The theory is also applied to the Hg 1-x Cd x Te materials and devices. Because of the very low effective masses involved, the theory predicts values as high as 2 × 10-4-2 × 10-5, depending on x . What remains presently unexplained are the high values of α H for semiconductor resistors and long p-n diodes.

The Hooge parameters of n + -p-n and p + -n-p silicon bipolar transistors

We establish here again the fact that the Hooge parameters of NEC57807 n⁺-p-n and in GE82 p⁺-n-p silicon bipolar transistors are orders of magnitude smaller than the value 2 × 10^-3postulated earlier. In the NEC57807 devices neither the base 1/<tex>f</tex>noise nor the collector 1/<tex>f</tex>noise is of the diffusion-fluctuation type. In the GE82 devices the collector 1/<tex>f</tex>noise is not of the diffusion-fluctuation type, but the base 1/<tex>f</tex>noise is of that type. We have given, also, a theory of the effects of surface recombination fluctuations in the emitter-base space-charge region on the base noise and the collector noise and find a noise spectrum that varies as<tex>I_\gamma</tex>where 0.5 < γ < 1.6 when going from small to large currents.We establish here again the fact that the Hooge parameters of NEC57807 n+-p-n and in GE82 p+-n-p silicon bipolar transistors are orders of magnitude smaller than the value 2 × 10-3postulated earlier. In the NEC57807 devices neither the base 1/ f noise nor the collector 1/ f noise is of the diffusion-fluctuation type. In the GE82 devices the collector 1/ f noise is not of the diffusion-fluctuation type, but the base 1/ f noise is of that type. We have given, also, a theory of the effects of surface recombination fluctuations in the emitter-base space-charge region on the base noise and the collector noise and find a noise spectrum that varies as I_\gamma where 0.5 < γ < 1.6 when going from small to large currents.

1/f noise in n+-p-n microwave transistors

Abstract 1/ f noise measurements in the base current and the collector current of NEC 57807 n + - p - n microwave transistors show that the noise is not of the mobility fluctuation type, since the current dependence of S I R ( f ) and S I C ( f ) differs from the theoretical predictions. The low collector current 1/ f noise makes it doubtful whether the mobility fluctuation concept is applicable in this case.

Low-frequency noise in Gallium Arsenide MESFETs☆

Abstract We observed the noise spectrum of GaAs MESFETs from 1/ƒ noise through diffusion noise ( 1/ƒ 1.5 spectrum) to thermal noise in the frequency range from 20 Hz to 2 MHz. At negative gate bias and floating drain the drain shows thermal noise, but when the gate is biased positively so that it draws gate current it will contribute excess noise to the floating drain. The current noise spectrum S I (ƒ) at both the gate and the floating drain shows an I 2mV 1 V relationship, which is common for the Schottky barrier diodes.

Instabilities in MODFET's and MODFET circuits

We report some instability phenomena of modulation-doped field effect transistors (MODFETs). It can be caused by traps or by high-frequency oscillations. By the improvement of technology to reduce the trap density and careful circuit layout we can reduce the noise level in the high drain voltage region.

Low-frequency diffusion noise in GaAs MESFET's

We report here on low-frequency diffusion noise of GaAS MESFETs. The Poole-Frenkel effect gives a shift of the corner frequency (f = D/πL2). From the measurements the activation energy of the diffusing ions is found to be 0.16 eV. At 77 K the diffusion noise is frozen out and the device has a 1/f spectrum.

Low-frequency noise in permeable base transistors

The predominant noise is<tex>1/f</tex>noise and consists of two parts: a) Noise varying as<tex>I\min{C}\max{2}</tex>, generated mostly with conducting channel and predominating for normal values of the collector voltage V<inf>CE</inf>. b) Noise at low V<inf>CE</inf>and practically independent of V<inf>CE</inf>; it is generated chiefly in the space charge region around the base grating and gives collector<tex>1/f</tex>noise at<tex>V_{CE} = 0</tex>. The turnover frequency of the first noise source lies at about 20 MHz for<tex>V_{CE} = 0.30</tex>V,<tex>V_{BE} = 0.20</tex>V. At sufficiently high frequencies the PBT shows thermal noise of the output conductance<tex>g_{c0}</tex>at zero bias. Generation-recombination noise is observed at large V<inf>BE</inf>and low V<inf>CE</inf>and comes mostly from the space charge region around the base grating.

Low-frequency noise spectra in MOSFETs made by the DMOS process

Low-frequency spectra of SD-211 and SD-212 made by the DMOS process are reported they show 1fβ spectra with β = 1 at low frequencies and β = 0.76–0.85 at high frequencies. At dry ice temperature a spectrum 1f0.55 appears at high frequencies which may indicate a one-dimensional diffusion noise process. At liquid nitrogen temperature the spectrum is 1f1.0 throughout; apparently the spectral components 1fβ with β < 1 have been frozen out. This may indicate that these spectral components are associated with ions or dislocations.

Noise in Permeable Base Transistors (PBTs)

Abstract We discuss in this paper the low-frequency noise and the high frequency operation PBTs. For an enhancement mode devices the noise is 1/f noise with a turn-over frequency of 20–30 MHz, for the depletion mode device the turnover frequency is much larger. The noise at constant VBE varies as IC2 for low VCE as expected for any fluctuating resistor or FET. The noise at constant VCE decreases rapidly with increasing VBE due to electron injection from the source. At high frequencies the noise should be thermal noise. A cut-off frequency fT can be defined; at that frequency the minimum noise figure is less than 6dB. Finally fT is expressed in terms of device parameters.

The Hooge parameters for n- and p-type Hg 1-x Cd x Te

The values of the electron effective mass<tex>m_{e*}</tex>in Hg<inf>1-x</inf>Cd<inf>x</inf>Te have been calculated for<tex>x</tex>= 0.20, 0.30, 0.40. Using the Debye temperature θ<inf>D</inf>for CdTe, the values of the Hooge parameter for Hg<inf>1-x</inf>Cd<inf>x</inf>Te have been estimated as a function of<tex>x</tex>and the temperature<tex>T</tex>. In view of the uncertainty in θ<inf>D</inf>, the estimate is probably correct within a factor of 2-3. We have also directly calculated θ<inf>D</inf>for Hg<inf>1-x</inf>Cd<inf>x</inf>Te and its associated Hooge parameters as a function of<tex>x</tex>; except for a possible temperature dependence of θ<inf>D</inf>, the results should be correct near room temperature.