C.M. Van Vliet

Quantum 1/f noise associated with ionized impurity scattering and electron-phonon scattering in condensed matter

Abstract Scattering of charged particles is accompanied by the emission of soft photons. Handels theory of 1/f noise, based on the infrared quasi-divergent coupling of the system to the electromagnetic field, indicates that the current associated with a beam of scattered particles will exhibit 1/f noise. His derivation is valid in a vacuum. Here we extend his results and obtain the fluctuation spectrum for the fluctuations in cross-section and for the scattering rates w kk′ in k-space, using the Born approximation. Next we consider mobility fluctuations due to these scattering rates, employing the relaxation time solutions of the Boltzmann transport equation, valid in non-degenerate semiconductors. Explicit results are obtained for the mobility-fluctuation noise caused by ionized impurity scattering, acoustic phonon scattering, optical phonon scattering, polar optical phonon scattering, and intervalley scattering. We derive Hooges law, and the Hooge parameters for the above-mentioned processes are obtai...

Decomposition of generation-recombination noise spectra in separate Lorentzians

Abstract The two characteristic quantities determining the Lorentzian-shaped g-r noise spectrum are the plateau value and the corner frequency. A condition is derived under which these quantities calculated for an exact two-trap level model can be approximated by a model in which the traps interact independently with the conduction band. If the Fermi level is few kT away from the levels considered and if the number of free carriers is larger than the number of traps, that condition is fulfilled.

Noise in near-ballistic n+nn+ and n+pn+ gallium arsenide submicron diodes

Abstract Direct-current (d.c.) characteristics and noise measurements in the range 1 Hz-25 kHz are reported for n + nn + and n + pn + near-ballistic devices, with n regions ( p regions) of 0.4 μm (0.45 μm), fabricated by molecular beam epitaxy at Cornell. The n + nn + mesa structures show very low 1/ƒ noise. indicating a Hooge parameter α H = 6.0 × 10 − . This very low noise is attributed to the near absence of phonon collisions. The thermal (− like) noise above 1 kHz is equal to Nyquist noise at the lowest currents, rising to slightly above Nyquist noise for high currents, indicating the presence of carrier drag effects. The n + pn + noise, on the contrary, is quite high. It seems to be associated with the ambipolar effects occurring for low injection of electrons in the p region. The importance of noise measurements for confirming ballistic or near-ballistic behavior is discussed.

Observation of single‐carrier space‐charge‐limited flow in nitrogen‐doped α‐silicon carbide. I. I‐V characteristics and impedance

This paper first reviews the properties of silicon carbide, in which polytypism is a salient feature. If a highly compensated insulating polytype is sandwiched between low resistive polytypes, space‐charge injection will occur. The theory of space‐charge‐limited current flow in the presence of traps is reviewed and a somewhat different version of the standard theory is presented, which shows more clearly the ohmic and space‐charge‐limiting regimes. Close analytical parametric forms for I and V are obtained. Experimental data on I‐V characteristics and impedance are presented for 52–300 K. Except at the highest temperature, four regimes are clearly visible in the I‐V curves. A quantitative comparison with the theory is made and various transport quantities for α‐SiC are deduced.

Observation of single‐carrier space‐charge‐limited flow in nitrogen‐doped α‐silicon carbide. II. Electrical noise

Noise spectra of α‐SiC in the presence of space‐charge‐limited flow are attributed to trapping noise. In the ohmic regime, SΔI∝ I20 and in the ohmic and low‐voltage quadratic regime SΔI∝I0‖V0‖ as required by the theory. The trapping levels are determined from the slope of the time constants versus 1/T; the results are in fair agreement with those obtained from the current‐voltage characteristic. The magnitude of the noise requires a modulation mechanism, such as caused by mobility fluctuations in the temperature range where ionized impurity scattering dominates.

Partition 1ƒ noise in pentodes and its quantum interpretation

Errors will occur in the determination of partition 1ƒ noise in pentodes, when the cathode 1ƒ noise is distributed between screen grid and anode in a manner different from the distribution of the ac signals. Tests show that such errors do exist, but usually they are not very large. A more accurate discussion of the Van der Ziel-Handel quantum 1ƒ noise model yields a correction to the formula for the partition noise spectrum Sp(ƒ) by a factor of about 0.85. Additional partition 1ƒ noise experiments are reported that fit reasonably well with the quantum 1ƒ noise theory. The partition 1ƒ noise of 6EC6 tubes seems to be a factor 5 larger than the quantum 1ƒ noise theory allows; it is most likely of non-quantum origin.

Partition 1/f noise in vacuum pentodes

Abstract Measurements are reported on partition 1/ f noise in pentodes. The masking cathode 1/ f noise fluctuation was sufficiently reduced by a feedback resistor R c in the cathode lead to make the partition noise accurately measurable. With the resistor R c in place, it was demonstrated with a transformer experiment that the remaining noise was almost exclusively partition 1/ f noise. Combining Handels quantum noise expressions for space-charge-limited diodes and triodes, some general considerations, and the experimental data, we were able to find an empirical expression for the pentode partition 1/ f noise that can accurately describe the data.

1/f noise in mobility fluctuations and the boltzmann equation

Abstract The 1/f noise in mobility and diffusivity are discussed. The two noise densities are related due to an instantaneous Einstein relation, valid for times larger than the collision time. The Boltzmann equation treatment shows that Hooges relation for the collective band mobility noise, Sμ(f)/( μ )2 = α/fN, can be justified for a nondegenerate and spatially noncorrelated electron or ion gas.

HOT ELECTRON DIFFUSION NOISE ASSOCIATED WITH INTERVALLEY SCATTERING IN SHORT GaAs DEVICES

The velocity fluctuation noise of a low impedance, 1.1 μm N + N − N + GaAs device is measured as a function of applied bias voltage employing a tuned step-up transformer. The experimental results are expressed in terms of the electron mobility and diffusion coefficient, and agree with Monte Carlo simulation data.

QUANTUM 1/F NOISE IN SOLID STATE SCATTERING, RECOMBINATION, TRAPPING AND INJECTION PROCESSES

The unified description of quantum 1/f noise in all elementary process rates and cross sections of electric transport processes in solids presented in 1982 is further developed in the present paper. 1/f fluctuations in the mobility, diffusion constant, surface and bulk recombination speed, tunneling and trapping rate are all derived from the same fundamental formula in terms of the fine structure constant.