Kostas Amberiadis

Carrier distribution and low-field resistance in short n + -n - -n + and n + -p - -n + structures

In the present paper, we calculate the potential, field, and carrier distributions in short n⁺-n^--n⁺and n⁺-p^--n⁺devices and estimate the low-field resistance. The results of the calculations present a set of universal curves which may be used to find the minimum carrier density in the sample, the barrier height, the electric field at the boundary, etc. Our calculations show that electron injection becomes very important when the doping level is smaller than 1.5 × 10¹⁴(cm^-3). (T/300 K)/ L²(µm) for GaAs diodes, where<tex>L</tex>is the sample length. The low-field resistance of the sample is limited by the thermionic emission of the sample and by the diffusion and drift in the sample. The thermionic emission dominates at low temperatures, in short samples, and the diffusion-drift dominates in longer samples at higher temperatures. The experimental values of low-field resistance for GaAs 0.4-µm n⁺-n^--n⁺devices at 77 and 300 K are in good agreement with the predicted values. The agreement is not so good for 0.25-µm devices and for n⁺-p^--n⁺devices. In the latter case, the disagreement may be due to uncertainty in the doping level because the low-field resistance of the n⁺-p^--n⁺structure is shown to be very sensitive to the doping level of the p-region.

Noise phenomena associated with dislocations in bipolar transistors

Abstract The effect of emitter-edge dislocations on the low-frequency noise of bipollar transistors was studied via phosporus surface concentration. A threshold in both noise factor and dislocation density was observed for surface concentration greater than 4.3 × 10 20 cm −3 . It has been found that the dislocations affect the noise considerably when their density is in excess of 10 6 cm −2 .

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

Abstract Noise measurements conducted on npn bipolar transistors have revealed that the emitter-edge dislocations give rise to both 1 f and g-r noise, the resulting noise increasing with the number of dislocations. In dislocated devices, an α ⋍ 1.8 × 10 −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.

Oscillator with odd- symmetrical characteristics eliminates low-frequency noise sidebands

Low-frequency noise in an oscillator normally produces two LF noise sidebands around the center frequency f_{0} of the oscillator. It was shown experimentally that these noise sidebands can be eliminated by using an oscillator circuit with an odd-symmetrical characteristic. A simple theory based on the van der Pol approach to oscillators can explain the observed effects.

Channel length dependence of the 1/f noise in silicon metal‐oxide‐semiconductor field‐effect transistors. II. Verification of the acceleration 1/f noise process

A systematic study of the 1/f noise dependence on the channel length in p‐ and n‐channel silicon MOSFETs (metal‐oxide‐semiconductor field‐effect transistors) is presented. Devices made by the same procedure on the same chip were used. In this way, the nonuniformity of noise sources, which strongly depend on the fabrication procedure (like 1/f noise produced by surface trapping), was avoided. Hooge’s parameter αH was used as a measure of the magnitude of the 1/f noise in the device. The αH was found to vary as the square of the channel length in p MOSFETs and in the most of the n MOSFETs. Existing theories and known noise mechanisms do not explain this dependence. The incorporation of a recent theory involving the acceleration 1/f noise in semiconductors, developed by van der Ziel, explains the experimental data very well. The αH was found to be independent upon the electric field and the extraction of an effective time constant was used for comparison between theory and experiment.

Effect of trap distribution on g-r noise spectra

Abstract The carrier number fluctuations in semiconductors and insulators with traps distributed uniformly across the energy band gap are calculated at thermal equilibrium. It is found that in both insulators and semiconductors the noise spectra always follow a behavior comparable to the g - r noise of a single recombination level. Furthermore, from the derived curves it can be concluded that a uniform distribution of traps, where the traps are allowed to interact with all the free carriers, is not a source of 1 f noise in semiconductors or insulators.

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

Abstract Noise measurements in p-type diffused and ion-implanted MOS capacitors were conducted. It was found that there are three sources of 1/ƒ noise: (1) number fluctuation 1/ƒ noise. It is due to the interaction of holes with the surface oxide. (2) Bulk mobility fluctuation 1/ƒ noise. It is due to the fluctuation in the bulk mobility. (3) Modulation 1/ƒ 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 1/ƒ 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 1/ƒ fashion.

Noise in VLSI

Publisher Summary This chapter discusses various spontaneous noise sources in very large scale integration (VLSI) circuits and their effect on circuit operation. It discusses these noise sources themselves, such as thermal noise in metal-oxide-semiconductor FETs (MOSFETs), shot noise and burst noise in bipolar transistors, flicker noise in MOSFETs, and bipolar transistors. It discusses the effect of very high frequency noise in MOSFETs and bipolar transistors, the effect of burst noise in bipolar circuits, and the effect of 1/ f noise in MOSFET and bipolar VLSI circuits. A MOSFET has a conducting channel capacitively coupled to the gate. At very high frequencies, the noise in the channel gives rise, because of the capacitive coupling to the gate, to a gate noise current. This is called induced gate noise. Cross talk can be defined as the undesirable coupling of energy between signal paths. In VLSI circuits, cross talk appears from two main sources—capacitive or inductive coupling between lines or elements, and common impedance coupling in the ground and battery lines. In these circuits, the interconnection paths are extremely dense and cross talk can be a significant problem.

g-r noise spectra of semiconductors and insulators with various trap distributions

We examine spectra of semiconductors and insulators with Gaussian and exponential energy distributions of traps. In both cases the noise spectra strongly resemble the g-r noise of a single trap level that can communicate with either the conduction or the valence band. It is noted here that in semiconductors the number of carriers is larger than the number of traps, while in insulators the opposite is true

Low-frequency noise due to carrier recombination in a p-n junction

Abstract The noise due to recombination in the space-charge region of an abrupt Si p - n junction is calculated numerically for low and moderate forward bias. Then an expression is given for the recombination noise in the bulk region at high injection. The results show that the low frequency ratio ξ(0) of the equivalent shot-noise current to the recombination current depends both on doping density and on injection level. The value of ξ(0) approaches 1 asymptotically for low and high injection independently of the doping level, and its minimum is near 0.75 in the case of a relatively highly doped diode at moderate injection. Finally the numerical values of ξ(0) are compared with the analytically estimated values as well as the experimental results.