E.R. Chenette

Noise in Solid State Devices

Publisher Summary The purpose of this chapter is to present a survey of noise in solid-state devices. This chapter also discusses the various noise sources and this is applied to p-n junction diodes, Schottky barrier diodes, tunnel diodes, Josephson junctions, bipolar transistors, junction field effect transistors (JFETs), and metal-oxide-semiconductor field effect transistors (MOSFETs) The most important sources of noise in solid-state devices are thermal noise, shot noise, generation-recombination (g-r) noise, and flicker noise. Moreover, for semiconductor material one encounters noise due to the generation and recombination of carriers. It shows up as fluctuations in the resistance of the sample that can be detected, in turn, by applying a voltage to the sample and measuring the fluctuating current. For simple cases, the noise can be described by one fluctuating number of carriers; either electrons or holes. This is true for the noise due to traps, deep-lying donors or acceptors, Shockley-Read-Hall centers when there is a predominant lifetime.

Investigation of the transition from tunneling to impact ionization multiplication in silicon p-n junctions

White noise spectra of diodes breaking down between 1·5 and 5 V have been used to investigate the details of the transition from tunneling to avalanche breakdown in silicon p-n junctions. It is found that the transition and carrier multiplication in these junctions is dominated by the influence of the threshold energies for ionization. Because this influence is not explicitly taken into account in the existing theories of carrier multiplication and noise, they are not applicable to low breakdown voltage diodes. Consequently, a multiplication onset model and alternate schemes for calculating the DC multiplication and noise in low breakdown voltage diodes are developed. Analysis of the noise data indicates that the threshold energies for ionization depend slightly on junction widths and, for the diodes employed in this study, range between 1·66–1·9 eV for electrons and 1·79–2·04 eV for holes. The minimum distance between ionizing collisions is found to range from 190 to 240 A for electrons and 200 to 250 A for holes. Application of the threshold energies for ionization to the multiplication onset model permits evaluation of the doping densities on both sides of the step junctions. From it, it is determined that the solubility of aluminum in silicon is NA = 9·5 ± 0·5 × 1018 cm−3.

Neutron-induced noise in junction field-effect transistors

A modified depletion-layer generation-recombination (g-r) noise theory is given for defects with energy levels away from the middle of the band gap. Measurements are presented on JFETs irradiated with neutrons. The g-r noise spectra of these indicate that five distinct defects are introduced; the results are explained with the modified theory.

Preliminary assessment of electrothermomagnetically loaded composite panel impact resistance/crack propagation with high-speed digital laser photography

This reports documents the baseline development of high-speed laser photography based assessment technique to determine effects of material resistance to puncture or fracture. A series of ballistic experiments were performed to at the Dynamic Event Imaging Laboratory at the Munitions Directorate, Air Force Research Laboratory site at Eglin, AFB, Florida. These experiments were performed to assess the effectiveness of laser photography to document the formation and propagation of cracks in composite materials with and without electromagnetic loading. These experiments were the first fully operational use of a novel and unique experimental capability for high-speed digital laser photography. This paper details the development of the experimental procedures and initial results of this exciting new tool. This report documents the experiments performed and the instrumentation developed along with recommendations for additional research.

Transistor noise at low temperatures

It is shown that the shot noise theory of transistors holds for low temperatures in alloy junction transistors, provided that the effect of hole-electron pair recombination in the emitter transition region is taken into account. The discrepancy between theory and experiment reported by Lee and Kaminsky can be accounted for by the fact that this process was ignored.

Base resistance measurements on bipolar junction transistors via low temperature bridge techniques

Abstract Accurate measurements of ohmic base resistance for bipolar junction transistors at low frequencies and for medium to low-bias conditions are somewhat difficult to obtain. Presented herein is a technique involving measurement of the input common-emitter hie parameter at cryogenic temperatures (where the intrinsic input resistance parameter is quite small) using conventional low-frequency bridge techniques. Comparison of results obtained by this procedure are made with results obtained by the input impedance circle diagram method and the noise figure method.

Noise effects in bipolar junction transistors at cryogenic temperatures: Part II

In Part II of this investigation, a characterization of the output noise current generator i0of modern planar bipolar junction transistors (BJTs) for common-base configuration with the input ac open circuited is developed and verified at temperatures ranging from 60 to 300 K. It is shown that at low temperatures, for those devices where recombination processes in the emitter-base space-charge region become very pronounced, the resulting noise for these processes shows less than full shot noise. This noise reduction can show up at temperatures slightly below room temperature for such devices. (Generation-recombination effects described in Part I may still become important at temperatures below 110 K.) Also, it is demonstrated that an important parameter to monitor in taking these measurements, at least at low temperatures, is the alpha cutoff frequency fα if the low-frequency theory is to be realized.

The effect of hot spots on the noise characteristic of large-area bipolar transistors☆

Abstract Measurements indicate that when hot spots are formed in large-area silicon power transistors, the 1 f noise increases and a new noise component with a 1 f 2 spectrum shows up. The increase in 1 f noise is attributed to the decrease in effective device area when the hot spot is formed. The noise with a 1 f 2 spectrum is attributed to a thermal feedback effect in the hot spot.

Current noise in surface layer integrated resistors

The excess noise ratio n−1, defined as the excess noise intensity over the thermal noise intensity, is used as a parameter for characterizing the current noise of integrated resistors. Theoretically n−1 is proportional to the square of the device current, inversely proportional to the square of the device width, and independent of the device length. This is well verified by experiment. The noise spectrum is of the form 1ƒα with α practically equal to unity, as expected for flicker noise. The effect of current crowding near the current-carrying contacts is investigated.

Induced gate noise in MOS FET's

Abstract Input admittance, drain noise and induced gate noise measurements are reported on several MOS FETs 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 als 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 g11 varies as ƒ 3 2 in MOS-units with gate overlap whereas g11 varies as ƒ2 in MOS-units with no gate overlap. There is at present no satisfactory explanation for this difference; an ƒ2 frequency dependence is expected theoretically.