Increase In Low-frequency Noise Research Articles

Dark current and 1/f noise in forward biased InAs photodiodes

Dark current and low-frequency noise have been studied in forward biased InAs photodiodes within the temperature range 77…290 K. Photodiodes were fabricated by diffusion of Cd into n-InAs single crystal substrates. It has been shown that, at the temperatures >130 K, the forward current is defined by recombination of charge carriers with participation of deep states in the middle of band gap. At these temperatures, a correlation is found between forward current and 1/f noise. At lower temperatures, the forward current and noise have been analyzed within the model of inhomogeneous p-n junction caused by dislocations in the depletion region. The experimental evidence has been obtained that multiple carrier tunneling is the main transport mechanism at low temperatures, which leads to an increase in low-frequency noise.

Total ionizing dose effects in junctionless accumulation mode MOSFET

In this paper, an extensive investigation of low-frequency (1/f) noise and total ionizing dose–response of junctionless accumulation mode double-gate (JAM DG) MOSFET is presented. Current–voltage (Id–Vg) characteristics and low-frequency noise of JAM DG MOSFET are simulated at different ionized doses and compared to different gate oxide thickness and different channel doping concentrations. A significant amount of irradiation-induced threshold voltage shift and increase in low-frequency noise is observed for different gate oxide thickness and channel doping concentration. Moreover, the irradiation-induced border trap densities are also obtained at different doses. The gamma radiation model of Sentaurus TCAD is used to get the required results.

Low-Frequency Noise in Light-Emitting Diodes Based on InGaN/GaN Quantum Wells under Electric Actions Accompanied with an Increase in the External Quantum Efficiency

The results of testing the degradation of light-emitting diode structures with InGaN/GaN quantum wells are reported. An increase in the external quantum efficiency as compared to the initial value is observed after the passage of current of 150–170 mA. Possible physical processes leading to a change in the quantum efficiency and an increase in low-frequency noise are considered.

Низкочастотный шум в светодиодах на основе InGaN/GaN квантовых ям при электрических воздействиях, сопровождающихся возрастанием внешней квантовой эффективности

The results of testing the degradation of LED structures with InGaN/GaN quantum wells are presented. An increase in the external quantum efficiency above the initial value was observed after passing a current of 150–170 mA. Possible physical processes leading to a change in quantum efficiency and an increase in low-frequency noise are considered.

Jet-installation noise and near-field characteristics of jet–surface interaction

The link between jet-installation noise and the near-field flow features of the corresponding isolated jet is studied by means of lattice-Boltzmann numerical simulations. The computational set-up consists of a flat plate placed in proximity to a jet, replicating the interaction benchmark study carried out at NASA Glenn. Installation effects cause low-frequency noise increase with respect to the isolated case, mainly occurring in the direction normal to the plate and upstream of the jet's exit plane. It is shown that the Helmholtz number, based on the wavelength of eddies in the mixing layer and their distance to the plate trailing edge, predicts the frequency range where installation noise occurs. Based on the isolated jet near field, scaling laws are also found for the far-field noise produced by different plate geometries. The linear hydrodynamic field of the isolated jet shows an exponential decay of pressure fluctuations in the radial direction; it is shown that the far-field spectrum follows the same trend when moving the plate in this direction. In the axial direction, spectral proper orthogonal decomposition is applied to filter out jet acoustic waves. The resultant hydrodynamic pressure fluctuations display a wavepacket behaviour, which can be fitted with a Gaussian envelope. It is found that installation noise for different plate lengths is proportional to the amplitude of the Gaussian curve at the position of the plate trailing edge. These analyses show that trends of jet-installation noise can be predicted by analysing the near field of the isolated case, reducing the need for extensive parametric investigations.

Investigation of Negative Bias Temperature Instability Effect in Partially Depleted SOI pMOSFET

The negative bias temperature instability (NBTI) mechanisms for Core and input/output (I/O) devices from a 130 nm partially-depleted silicon on insulator (PDSOI) technology are investigated. The I/O device degrades more than the Core device under the same stress electric field due to the different gate oxide processes in these two types of devices. Both the oxide trap charge and interface trap lead to the transfer characteristics degradations of the device after NBTI. While the near interfacial traps result in the increase of low frequency noise (LFN). The trap densities near the silicon/gate oxide interface introduced by stress are extracted using the LFN method. NBTI-induced gate current increase is observed for Core device, but not for I/O device. It is result from the enhanced tunneling process, which is induced by the increase of electric field in the gate oxide after charge trapping at or near the channel interface. The gate width and length dependences of NBTI are observed. The enhanced NBTI degradation observed in short channel and narrow channel device is result from the enhanced NBTI effect at channel edge regions. The larger hole concentration is a main cause of the more serious NBTI degradation at the channel edge regions, including the nearby region of STI sidewall along the channel width direction and the gate edge region along the channel length direction. This conclusion is also verified by the TCAD simulations.

Noise Reduction in Supersonic Jets Exhausting over a Simulated Aircraft Carrier Deck

An innovative noise reduction method for supersonic exhaust jets was studied in a model-scale aircraft carrier environment. Acoustic measurements of model exhaust jets with (and without) distributed blowing, producing “fluidic inserts,” were performed. The model carrier environment consisted of a ground plane of adjustable distance below the jet, and a simulated jet blast deflector similar to those found in practice. The noise reduction of fluidic insert jets, above a ground plane, with steering of the “quiet planes” was examined with heat-simulated jets using near- and far-field pressure measurements. For jets exhausting over a ground plane, the fluidic inserts reduced the overall sound pressure level by 3–5 dB in the direction of maximum noise radiation. Upstream and sideline angles showed very little or no increase in sound level. Jets impinging on a modeled jet blast deflector were tested in addition to jets solely in the presence of a ground plane. The deflector resulted in downstream acoustic shielding and an increase in low-frequency noise. The region of maximum noise radiation for heat-simulated jets from nozzles with fluidic inserts impinging on the jet blast deflector was reduced in level by 4–7 dB. This region includes areas where carrier personnel are located.

Total Ionizing Dose Radiation Effects in the P-Type Polycrystalline Silicon Thin Film Transistors**Supported by the National Natural Science Foundation of China under Grant Nos 61574048 and 61204112, the Science and Technology Research Project of Guangdong Province under Grant Nos 2015B090912002 and 2014A030313656, and the Pearl River S&T Nova Program of Guangzhou.

The total ionizing dose radiation effects in the polycrystalline silicon thin film transistors are studied. Transfer characteristics, high-frequency capacitance-voltage curves and low-frequency noises (LFN) are measured before and after radiation. The experimental results show that threshold voltage and hole-field-effect mobility decrease, while sub-threshold swing and low-frequency noise increase with the increase of the total dose. The contributions of radiation induced interface states and oxide trapped charges to the shift of threshold voltage are also estimated. Furthermore, spatial distributions of oxide trapped charges before and after radiation are extracted based on the LFN measurements.

A trial application of acoustic excitation for jet noise reduction

Jet noise, one of the dominant noise components from an aircraft jet engine is known as the result of developed vortices produced during jet mixing process. In last couple of years, a method for jet noise reduction which acoustically controls the jet mixing layer using a sound excitation is proposed and investigated under the collaboration between The University of Tokyo and JAXA. In this paper, the main idea, experimental apparatus, experimental condition and experimental results will be explained. The experiment was conducted under an unheated and subsonic jet condition. The results show that low frequency sound excitation results in an increase in low frequency noise and a decrease in high frequency noise. The low frequency sound excitation is considered to excite the instability of jet flow and collapse the jet plume. On the other hand, the high frequency sound excitation resulted in a slight increase of high frequency noise and a slight decrease of low frequency noise (0.5 dB reduction in maximum) si...

Impact of granular work function variation in a gate electrode on low-frequency noise for fin field-effect transistors

The impact of work function variation (WFV) in a metal gate (MG) electrode on low-frequency noise (LFN) is revealed for fin field-effect transistors (FinFETs). The LFN level is compared between the FinFETs having polycrystalline TiN and amorphous TaSiN MGs. The amorphous TaSiN MG exhibits a marked suppression of flicker noise in comparison with the TiN MG. The difference in the LFN level is correlated with the threshold voltage variability reflecting the WFV of the MG. By modeling the WFV of the TiN MG in the FinFET structure by three-dimensional device simulation, we clearly reveal the mechanism of the LFN increase by the WFV.

Experimental assessment of anomalous low-frequency noise increase at the onset of Gunn oscillations in InGaAs planar diodes

In this work, the presence of anomalous low-frequency fluctuations during the initiation of higher frequency oscillations in InGaAs-based Gunn planar diodes has been evidenced and investigated. Accurate measurements showing the evolution of the power spectral density of the device with respect to the applied voltage have been carried out. Such spectra have been obtained in the wide frequency range between 10 MHz and 43.5 GHz, simultaneously covering both the low-frequency noise and the fundamental oscillation peak at some tens of GHz. This provides valuable information to better understand how these fluctuations appear and how these are distributed in frequency. For much higher frequency operation, such understanding can be utilized as a simple tool to predict the presence of Gunn oscillations without requiring a direct detection.

Measurements of Low Frequency Noise of Infrared Photo-Detectors with Transimpedance Detection System

Abstract The paper presents the method and results of low-frequency noise measurements of modern mid-wavelength infrared photodetectors. A type-II InAs/GaSb superlattice based detector with nBn barrier architecture is compared with a high operating temperature (HOT) heterojunction HgCdTe detector. All experiments were made in the range 1 Hz - 10 kHz at various temperatures by using a transimpedance detection system, which is examined in detail. The power spectral density of the nBn’s dark current noise includes Lorentzians with different time constants while the HgCdTe photodiode has more uniform 1/f - shaped spectra. For small bias, the low-frequency noise power spectra of both devices were found to scale linearly with bias voltage squared and were connected with the fluctuations of the leakage resistance. Leakage resistance noise defines the lower noise limit of a photodetector. Other dark current components give raise to the increase of low-frequency noise above this limit. For the same voltage biasing devices, the absolute noise power densities at 1 Hz in nBn are 1 to 2 orders of magnitude lower than in a MCT HgCdTe detector. In spite of this, low-frequency performance of the HgCdTe detector at ~ 230K is still better than that of InAs/GaSb superlattice nBn detector.

On timing jitter of mode locked Kerr frequency combs

We study fundamental timing jitter in repetition rate of a mode locked Kerr frequency comb generated in an externally pumped nonlinear ring resonator. We show that the increase in the integrated power of the comb harmonics, and the corresponding decrease of the duration of the associated pulse, results in the increase of low frequency noise, and a decrease in high frequency noise.

Measurement and control of aircraft landing gear broadband noise

Noise generated by aircraft landing gear is a major contributor to the overall airframe noise during landing approach of a commercial aircraft. Fairings covering geometrically complex areas of the gears have proved to be very effective in noise reduction, but in tests on an A340 main landing gear the overall benefits of the fairings were offset by an increase in low-frequency noise. In this study the measurement and control of broadband noise throughout the frequency range have been investigated using a 1/4 scale A340 main landing gear model that has been tested using a range of different measurement methods and wind facilities. Experiments were firstly conducted in a conventional closed-section wind tunnel using two phased microphone arrays mounted on the ceiling and sidewall of the tunnel respectively, and noise control strategies with modified fairings were developed. Noise tests were then performed in an open-jet aeroacoustic facility using far-field microphones to verify the wind-tunnel test results. Comparison between the two tests showed that the relatively smaller noise-reduction potential of the fairings measured in wind tunnel was due to the higher flow blockage of the tunnel. Nevertheless, the experiments indicated that the phased microphone arrays could be applied to measure the noise reductions achieved by noise control treatments with reasonable accuracy, especially in mid- and high-frequency range. The aeroacoustic facility test results were finally projected to full scale and compared to the full-scale model wind-tunnel test. Both results were shown to agree over a wide frequency range, indicating the validity of the tests on the 1/4 scale model.

Low Frequency Noise Correlation between Electrical and Optical Signals for Predicting Degradation in Organic Light Emitting Diodes

AbstractThe Low Frequency Noise (LFN) characteristics of Organic Light Emitting Diodes (OLEDs) were investigated in relation to device degradation. The standard layer structure of indium tin oxide (anode), hole transport layer, Alq3, Lithium Fluoride and Aluminium (cathode) was used. With duration of operation, the device degradation is characterized by an eventual drop in the luminance level and the electroluminescence efficiency. Additionally, the driving voltage at a fixed current and the LFN increase gradually during device degradation, accompanied with the formation of non-emissive areas (dark spots). It is found that the coefficient of correlation between voltage fluctuations across the device and low frequency fluctuations of the optical signals remains constant for an initial period and then decreases exponentially with duration of operation and is a sensitive parameter to predict OLED device lifetime. For a number of OLEDs driven at constant current, the device with higher initial correlation coefficient possesses a longer lifetime. The direct relation between LFN correlation and device lifetime can be explained by carrier recombination mechanisms at the microscopic level. An increase in trap density can reduce the internal radiative recombination rate which at the macroscopic level is reflected by a decrease in the correlation coefficient.

Electric Property Evolution of Structurally Defected Multilayer Graphene

We report on the influence of structural disorder on the electrical properties of multilayer graphene (MLG). Exponential decreases in the conductance and transconductance with increase of defects in the MLG were observed, which could be explained by the percolation and the variable range hopping conduction. An enhancement of p-type nature with increasing disorders was considered to be the result of oxygen doping in the graphene sheets introduced by oxygen plasma. The rapid increase of low-frequency noise was attributed to the formation of conductive network through the continuum percolation, as the low-frequency noise could be increased by the enhanced carrier scattering at the defect sites. We hope that our result should suggest a simple method of tuning the electrical properties of graphene.

Improvement of Noise Characteristics in Super-Resolution Near-Field Structure Disc

The research interest in super-resolution near-field structure (Super-RENS) technology is shifting from the signal intensity (carrier-to-noise ratio, CNR) to the signal uniformity (jitter or bER). To achieve uniform signal characteristics, it is important to reduce signal fluctuation in the super-RENS disc. In this study, we investigated the relationship between signal fluctuation and low-frequency noise (LFN), and analyzed the LFN increase in recording and readout processes. It was found that signal fluctuation had a close relationship with LFN. It was also found that certain recorded mark shapes, such a bubble shape, and high readout power increased the LFN during recording and readout processes of a super-RENS disc. Therefore, using non bubble-type recording material and low super-resolution readout material, we markedly improved the LFN of a super-RENS disc.

Polarization-resolved intensity noise in erbium-ytterbium codoped fiber lasers

The intensity-noise properties and polarization dynamics of a two-polarization Er:Yb codoped fiber laser are investigated and discussed. For a laser without polarization control, the low-frequency relative intensity noise reaches a minimum of approximately −90 dB/Hz. Polarization-sensitive detection reveals that the low-frequency intensity noise is influenced by a strong resonance associated with anticorrelated intensity fluctuations of the orthogonal linearly polarized modes. The frequency of the resonance varies linearly with laser power and leads to an increase in low-frequency noise of more than 45 dB for the polarized output of the laser.

Low-frequency noise and radiation response of metal-oxide-semiconductor transistors with Al2O3/SiOxNy/Si(100) gate stacks

Low-frequency noise and irradiation response are studied for n-channel metal-oxide-semiconductor field-effect transistors with Al2O3/SiOxNy/Si(100) gate stacks. Radiation-induced threshold-voltage shifts and low-frequency noise increase with dose and decrease with postirradiation annealing. The border trap density in the gate dielectric inferred from the noise measurements is significantly higher than that typically observed in thermal SiO2. Similarly, the effective radiation-induced-hole trapping efficiency in Al2O3 gate dielectrics is significantly higher than for SiO2 gate dielectrics of comparable thickness. The low-frequency noise in these high-κ devices can be described well by a number fluctuation model.

An anomalous device degradation of SOI narrow width devices caused by STI edge influence

The effects of shallow trench isolation (STI) on silicon-on-insulator (SOI) devices are investigated for various device sizes with three different gate shapes. Both NMOSFETs and PMOSFETs with the channel region butted to the STI show a reduction in mobility (NMOSFETs and PMOSFETs) and an increase of low-frequency noise as the channel width is reduced. In comparison, the devices without the STI-butted channel region show much less variation in mobility for various channel widths. The degradation of MOSFET yield in SOI MOSFETs with the STI is found to be dependent on the device width since the contribution of the interface roughness (or damage) between the STI and the channel formed during the dry etch process becomes significant with the decrease of channel width and the increase of channel length. From the charge-pumping results, the interface state (N/sub it/) generated by the STI process was identified as the cause of the anomalous degradation.