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The temperature dependence of the Hooge parameter alfaH for both n- and p-type InGaAs heterostructures with as-grown non-alloyed ohmic contacts shows good agreement with that estimated from the harmonic coupling model; alfaH is given by aa/lambda, where aa is the lattice constant and lambda is the mean free path of the semiconductor material. Experimental results for several other semiconducting materials normalized by the mobility ratio also verify the validity of the model. We are now able to estimate the Hooge parameter theoretically from only the material parameters, whereas the experimental results are scattered over several orders of magnitude.

RTS noise in MOSFETs is given by drain current fluctuation due to charge carrier capture and emission by a single active trap. From the drain voltage dependence of the ratio of capture tauC and emission tauE times the longitudinal trap position in the channel can be calculated. According to the Shockley-Read-Hall statistic, tauC is inversely proportional to the concentration of charge carriers n and in most noise papers, drain current ID is commonly supposed to be proportional to n and used to express concentration. Then we should expect tauC to decrease with increasing current, however, opposite dependence is usually experimentally found. In order to explain this discrepancy, we present a model of non-uniform charge carrier density distribution in channel with concentration decreasing towards the drain electrode.

The mobility and the carrier concentration of the epitaxial n-GaN are obtained experimentally as a function of the temperature between 300 and 15 K, and are found to be in good agreement with those derived from the numerical analyses assuming a certain amount of the compensation ratio. The sample available at present has a rather poor mobility compared with that expected from an ideal perfect crystal, and we must assume a comparatively large amount of the compensation in the numerical analyses. The typical 1/f noise characteristics are also observed by forming an ideal Ohmic contact to the devices at the optimum alloying temperature and its period. Based on the introduced amount carrier concentration and the mobility together with the contact conditions, the Hooge noise parameters are derived experimentally between 100 and 300 K. Experimental data reported so far are also summarized as a function of the normalized mobility.

The capacitance-voltage (C-V) characteristics of Al0.25Ga0.75N/GaN heterostructure barrier varactors (HBV) grown by metal-organic chemical vapor deposition on a c-oriented sapphire substrate were studied. The favorable material properties of wide-band-gap III-N's are important in realizing the HBVs for frequency triples and distributed line pulse sharpens for practical use. The HBV structure consists of a 10-nm-thick undoped Al0.25Ga0.75N barrier sandwiched between two undoped GaN layers with a thickness of 5 nm. The barrier structure is further sandwiched between two n-GaN (n = 5 × 1017 cm–3) layers with respective thicknesses of 500 nm and 1 µm to form the top and the bottom ohmic contacts. At room temperature, the C-V characteristics show a maximum capacitance Cmax at approximately –1.8 V because of the induced piezoelectric field within the heterostructure, and the I-V characteristics show an increase in leakage current below –1.5 V and above 0.5 V. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ohmic contacts are formed on the epitaxial n-GaN film by the electron beam evaporation of Ti/Al and their rapid thermal alloying with device separation by a fairly fast Electron Cyclotron Resonance (ECR) plasma etching. The etched surface has a poor ohmic contact with a typical contact resistance of 8.1 × 10 - 3 Ω.cm 2 , while the as-received and rinsed surface has a better contact with a lower contact resistance of 7.5 × 10 - 6 Ω.cm 2 . The resistivity of the film is determined as a function of the temperature, in good agreement with the numerical analyses. The ohmic characteristics are evaluated by the 1/f noise measurements. Low ohmic contacts give the typical 1/f noise characteristics which increase with the square of the sample current 1, while higher ohmic contacts give a linear noise power dependence on the sample current 1. We are able to evaluate, therefore, the ohmicity of the electrodes most sensitively from the 1/f noise measurements. Assuming the relevant total electron number between the electrodes, the Hooge parameter is estimated as α H = 5.3 x 10 - 6 at room temperature, in qualitative agreement with the cross correlational 1/f noise model.

A low frequency noise and charge carrier transport mechanisms were investigated on tantalum capacitors made by various producers. The model of Ta–Ta2O5–MnO2 MIS structure was used to give physical interpretation of I–V characteristics in normal and reverse modes. The noise in time and frequency domain was examined and noise sources were identified. We evaluated correlation between leakage current and noise spectral density and discussed corresponding quality and reliability indicators.

Transport and low frequency noise characteristics of In0.52Al0.48As/InxGa1-xAs heterostructures were measured in wide temperature range (15 K to 450 K) and experimental results compared with intrinsic 1/f noise models, estimating mobility fluctuations due to various scattering processes. The 1/f phonon energy partition fluctuation model predicts the value of Hooge parameter given as the ratio of the lattice constant and mean free path and several p-type and n-type samples reveal corresponding values of αH ≅ 0.5 and αH ≅ 4×10-3, respectively. Most of the lattice-matched n-type samples however give much lower αH of about 10-5 for temperature below 200 K, which is closer to the quantum 1/f noise theory limit. At elevated temperatures g-r noise was observed with trap activation energy 0.63 eV. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The InAs quantum well heterostructure was successfully grown on a semi-insulating GaAs substrate by MBE. On the GaAs substrate, the semi-insulating AlGaAsSb was grown to a thickness of 600 nm as the buffer layer, followed by a 15 nm InAs channel layer and a 35 nm AlGaAsSb doped layer together with 10 nm GaAsSb cap layer successively. The electron mobility and the sheet carrier concentration of the 15 nm InAs heterostructure was about 1 m2 V−1 s−1 and 4.5×1012 cm−2, respectively, at room temperature. This heterostructure is equivalent to the heavily doped InAs substrate with little change of the electron mobility on temperature. This device has typical 1/f noise characteristics without any large bulge throughout the frequency and the temperature ranges observed. The Hooge parameter was αH=1×10−3 at room temperature, decreasing monotonically with the decreasing temperature down to 5×10−4 at 50 K, indicating characteristics of the virtually constant mobility and constant carrier concentration device.

Low frequency noise characteristics of GaN/AlGaN HFET structures grown either on sapphire or SiC substrates were measured in wide temperature range 13 K to 300 K and activation energy of traps determined by several methods around 0.42 eV (SiC) and 63 meV (sapphire). Conceptual approach to trap parameters estimation was tested on RTS noise time-trace. The Hooge parameter alpha of GaN/AlGaN on SiC HFETs was of the order of 10-4 to 10-5, whereas two orders higher values for sapphire based devices were given by strong g-r noise.

The Hooge constant of p-Ge is shown consistent with the new quantum mechanical model, αH = α /λ the energy partition among coupled harmonic oscillation model in the equilibrium, exactly inversely proportional to the mean free path normalized by the lattice constant.

We fabricated the first ultrafast active transmission lines with low dielectric constant (low-k) polyimide integrated with ultrafast photoconductive switches formed by the nano-anodization process. Electrical pulses as short as 290 fs were measured on this transmission line by an electrooptic sampling system based on a femtosecond laser. P-n junctions were inserted in the transmission line to control dispersion in lines, and low-k polyimide was introduced to reduce dielectric and radiation losses.

DC leakage currents of MLCC (Multi Layerd Ceramc Capacitor)s show the typical Poole Frenkel relationship between the normalized current log (I/V) and the normalized voltage V within the specified voltage across the device without any local breakdown characteristics, giving the PF constants and the barrier heights of the insulating BaTiO 3 layers. The typical 1/f noise characteristics are also observed, and the normalized noise amplitudes are obtained as the function of the MLCC series resistance, noise amplitudes of which are found more than 60 dB larger than those of the metal resistors. Both the leakage current and 1/f noise amplitudes give time saving reliability information much faster than those of the conventional MTTF method. The emerging needs of the ecological vehicles or the two cycle motor inverter systems accelerate the development of the high voltage MLCCs sharing a large part of capacitor applications. Up to 80 % of the total capacitors are made now by the MLCC. The MTTF method is usually applied as the standard conventional reliability test for these capacitors. Both the leakage current and 1/f noise amplitudes give time saving reliability information much faster than those of the conventional MTTF method. The leakage current in MLCC can be explained by the Poole-Frenkel tunneling effect. The normalized current (I/V) is linearly dependent on SQRT(V), noise levels are 60 to 80 dB larger than those of the conventional carbon resistors, with typical 1/f characteristics, dependent on the lots and independent of the biasing voltage.

The critical layer thickness of n-In 0.52 Al 0.48 As/strained-In 0.8 Ga 0.2 As/In 0.52 Al 0.48 As grown on InP substrates was investigated by measuring the photoluminescence spectra. These pseudomorphic heterostructures grown by molecular beam epitaxy attained the highest mobility, 16,200 cm 2 /V·s, at room temperature. The photoluminescence emission intensity decreased in the thickness range of 20 to 25 nm for the In 0.8 Ga 0.2 As layer. These results indicate that the critical layer thickness of this structure follows the energy balance model rather than the mechanical equilibrium model. In addition, this critical value is in good agreement with the results based on the electron mobility behavior.

Random Telegraph Signal (RTS) noise was measured in submicron MOSFETs under various biasing conditions from sub threshold to inversion region and dependence of amplitude and mean time of capture and emission on electric field and electron concentration analyzed. Numerical model of charge carrier transport in the channel was used to estimate trap position between the source and drain electrodes from experimental characteristics.

A very high electron mobility pseudomorphic Si-doped In 0.48 Al 0.52 As/ undoped In 0.8 Ga 0.2 As heterostructure is successfully grown on the InP substrate by the newly invented technology of stabilizing the transient vapor flux of group-III cells with SQRT control and inserting an InAs monolayer in the heterointerface between the channel layer and the spacer. The actual critical thickness of the pseudomorphic heterostructure as determined by the Hall measurement is found to follow the energy balance model, and the highest 2DEG mobilities over 1.6 and 16 m 2 /V·s with 1.6×10 12 cm -2 at 293 and 10 K, respectively, are obtained for the InP-based pseudomorphic In 0.52 Al 0.48 As/In 0.2 Ga 0.2 As heterostructure.

A very high electron mobility pseudomorphic In0.8Ga0.2As heterostructure is successfully grown on InP both by the elimination of the overshoot of flux densities and by the precise control of the flux ratio through a new calibration technique of RHEED oscillations in an MBE system. The critical layer thickness for the pseudomorphic growth of InGaAs on InP is found to follow the energy balance model, and a very high 2DEG mobility of over 1.5 and 16 m2/Vs at 293 and 10 K, respectively, is obtained.

The drain voltage noise of commercial AlGaAs/GaAs HEMTs shows typical ƒ −1.0 noise characteristics with a Hooge noise parameter of about 6 × 10−5, while that of conventional GaAs MESFETs has a large GR noise bulge at about 15 Hz. The noise levels of the HEMT are smaller than those of the MESFET by 19 dB Hz−0.5 at the same bias conditions, manifesting the advantage of HEMT as a low-noise device.

Typical 1/ f noise was excited in quarter-micron filaments of both GaAs and InP which were successfully made by a focused ion-beam implantation. Their noise levels were observed to vary exactly as f −1.0 and increased in proportion to the square of the terminal voltages. The GaAs filament has a generation-recombination (GR) noise bulge at round 500 Hz, corresponding to the deep level activation energy of 0.6eV. The noise levels of the InP filament, on the other hand, decreased monotonically throughout the frequency ranges from 0.1 Hz to 100 kHz, indicating much less deep levels. The Hooge's noise parameters were evaluated exactly by the carrier numbers derived from the Hall measurement and 1/ f noise levels to be 4.5 × 10 −6 for the GaAs filament and 6.1 × 10 −6 for the InP one. These values are the smallest yet reported in these materials.

The capture and emission time constants dependence on drain current for constant gate voltage and variable drain voltage show that probability for charge carrier capture decreases with increasing lateral electric field while emission process is independent on lateral field intensity. We have performed analyses of SiO2 gate insulating layer from VA characteristics measured in wide temperature range (gate electrode area 1.5 μm2, insulating layer thickness 6 nm. Leakage current in reverse mode of n‐MOS sample (for gate electrode negative) is for applied voltage lower than 1 V exponential function of applied voltage with saturation current I0 = (1–3)×10−16 A and ideality factor near to 1. Saturation current value corresponds to Schottky barrier high about 1.2 eV. We suppose that in SiO2 gate insulating layer and on the interface Si‐SiO2 there are oxygen vacancies and interstitials. High density of overlapping energy localized states creates in SiO2 impurity conduction band about 1.2 eV above the Si conduction band. Between channel and interface Si‐SiO2 localized states exists g‐r stochastic exchange of electrons, which is a source of 1/f noise. Reducing the density of interface states by plasma oxidation leads to 1/f noise spectral density lowering. There exists electron exchange by tunnelling between interface Si‐SiO2 localized states and traps localized in gate insulating layer about lnm from channel. These quantum transitions are sources of RTS noise. Electron from channel trap can tunnel to interface Si/SiO2 localized state or it can enter through SiO2 impurity conductivity band to gate electrode by thermionic emission.

An instrument to improve power spectrum density (PSD) measurements, a highly sensitive preamplifier and a data acquisition unit are designed as well as a programmable power battery source. The preamplifier has 8 junction field effect transistor (JFET) inputs in parallel resulting in an input noise equivalent power of —186 dBV2/Hz. The data acquisition system consists of a low-pass filter, an A/D converter and a RAM, which transfer the data to the connected PC. The FFT or other signal processing is carried out within the PC. The battery power source is controlled by the PC, enabling us to obtain the device-under-test (DUT) bias DC required by the program. This measuring system works well at room temperature where the DUT and the power source could be put into a magnetic shielding box to reject spurious line noises. In the case where the DUT is placed in a cryostat to measure the temperature dependence of noise properties, however, the shielding of the DUT from the power line becomes a serious problem. Particularly in order to use a compressor cooling system, spurious noises come into the measuring system through the power lines of the compressor. In such a case the preamplifier must be placed as close as possible to the DUT, and the power line to the compressor is sometimes disconnected from the system.

This paper investigates the emission and capture kinetics of random telegraph signals (RTS) in Quantum dots and submicron MOSFET structures. Emphasis is laid on the signals showing a capture process which deviates from the standard Shockley-Read-Hall kinetics. The proposed model distinguishes between primary processes consisting in quantum transitions of electrons between traps and the conduction or valence band and secondary processes, consisting in current modulation. If the RTS noise sources are quantum transitions of electrons between a shallow trap and the conduction band then the primary process is one-dimensional and it coincides with the secondary process — current modulation. For deep traps the primary process is a two dimensional g — r process. It is shown in this paper how to distinguish experimentally between the one or two-dimensional primary processes by measuring the probability density of the occupation time in both current states. These long-time measurements require a very stable power source and active shielding of low frequency magnetic fields.

Important points in designing a low noise amplifier in very low frequency region such as around 1mHz are to avoid the coupling capacitor at the front end, and to suppress the thermal drift. Practical examples are described.

Offset voltage and its drift were suppressed by generating the weighted sum of multiple dc amplifiers. The weighting factors were determined so as to make the total gain and the signal‐to‐noise ratio as large as possible.

Noise characteristics of epitaxial n‐GaN on sapphire layers and GaN/AlGaN on sapphire or SiC HFET structures were investigated in the temperature range of 13K to 300K. Ohmic contacts were made using Ti/Al/Ni/Au and contact noise was found negligible by TLM analysis. The Hooge parameter αH of epitaxial GaN was 2×10−3 at 300K, gradually decreasing to 10−4 around 50K. For GaN/AlGaN on sapphire HFET the g‐r noise was dominant at almost every temperature, allowing only to determine αH=2×10−4 at 22K. The GaN/AlGaN on SiC HFETs were characterized by αH values of 10−4 to 10−5.

In Athena Olympics in 2004 a Japanese girl got the gold medal in Women Marathon games. Just before the beginning, she was listening to some domestic melodies in order to concentrate on the race. The rhythm or power of that music is found to have the typical 1/f noise characteristics. The 1/f music is found effective to concentrate as well as to relax themselves for a fairly long time range, while some short time trial runner uses a kind of white noise like music.

Low cost highly sensitive preamplifier was made by using the commercially available operational amplifier AD797 which has the input noise equivalent power of −190 dBV2/Hz with 80 dB amplification.

The downscaling of electronic devices makes high field transport effects more important. In deep submicron technology high transversal and high lateral electric field exists. Application of drain voltage 1V results in electric field, which exceeds the silicon critical electric field. Electron temperature is then higher than lattice one and field dependent electron mobility must be considered. Due to small gate area we were able to activate one trap only and then in time domain two levels signal was observed. A systematic analysis of two level RTS signal was made to obtain information on capture and emission processes as a function of gate voltage, drain current and temperature for low and high lateral electric field. With increasing drain voltage capture time increases, while dependence on gate voltage is almost the same as for low drain voltage. For constant gate voltage and variable drain voltage emission process is independent on lateral field intensity, while capture time increases with lateral field ...

A low frequency noise and DC leakage current measurements have been performed on the MIS structure NbO − Nb2O5 − MnO2. The mechanism of current flow and current noise sources were determined from these measurements. The insulating layer thickness is 50 to 150 nm, relative permittivity about 38. The charge is accumulated not only on NbO and MnO2 electrodes, but also in the Nb2O5 insulating layer. The charge carrier transport is determined by the Poole‐Frenkel mechanism and tunnelling in the normal mode (for NbO electrode positive). In this case g‐r noise is dominant for Poole‐Frenkel mechanism and 1/f noise is dominant for tunnelling.

RTS noise of Si MOSFETs and GaN HFET was analysed by means of zero cross method. Noise spectral density of crossing events in 1 ms to 100s windows was flat over 10−5 to 103 frequency range without apparent 1/f noise. The fluctuation of crossing rate was same in every sample, although other noise components next to RTS noise are quite different in Si and GaN devices. Correlation analysis of pulse length in doublets and triplets of successive pulses didn’t reveal any mutual dependence.

Movements of amoebas were automatically traced using the difference between two successive frames of the microscopic movie. It was observed that the movements were almost random in that the directions and the magnitudes of the successive two steps are not correlated, and that the distance from the origin was proportional to the square root of the step number.

In the present paper, emphasis is laid on those RTS showing a capture process, which deviates from the standard Shockley-Read-Hall kinetics. A modified two-step approach is proposed. In this case the charge carrier quantum transitions represent a primary process X(t), which involves two or three quantum states. The measurable quantity is the current modulation, which has discrete states, too. The current modulation is then represented by a secondary process Y(t). The proposed model can explain some of the complex switching phenomena being measured in nanoscale devices. The quadratic dependence of the capture rate on the current and the noise spectral density dependence on the current and temperature are analysed. It is shown that the occupation time probability density for emission is given by a superposition of two exponential dependencies, whereas the capture time constant distribution is purely exponential.

The trace of the gate noise voltage was successfully caught by the measurements of the correlation between the noise outputs of a pair of JFETs connected to a common gate resistor. It is shown for 2SK150 (n-channel junction FET) that the gate noise voltage is 1/f-type and its level is -142dbV 2 /Hz at 1Hz, and that the correlation coefficient between the gate noise voltage and the gate noise current is -1.

The Hooge parameters of compound semiconductors are found to be in inverse proportional to the mean free paths of materials. The newly developed model of 1/f phonon energy partition fluctuation in thermal equilibrium predicts the value of Hooge parameter as αH = a/λ, the ratio of the lattice constant a and the mean free path λ. Several reported experimental results on αH for very pure semiconductors are found on the a/λ line. Experimental verification is given by measuring noise in InGaAs/InAlAs heterostructure, where optical phonon effects can be observed due to negligible impurity scattering. The Hooge parameter of about 1 in p-InGaAs and 10-3 to 10-5 in n-InGaAs reflects the two order difference in the mobility and corresponding λ values.

We have fabricated ultrafast electrical waveguides with low-k polyimide integrated with ultrafast photoconductive switches formed by nano-anodization process for the first time. Electrical signals are affected by nonlinear capacitance of p-n junctions in this waveguides, and pass through the low-k polyimide, so the dielectric loss and the radiation loss are dramatically reduced. The electrical pulses as short as 290 fs were measured on this waveguide by an electro-optic sampling system based on a femtosecond laser.

The growth of a very high electron mobility pseudomorphic In/sub 0.8/Ga/sub 0.2/As heterostructure on InP using an overshoot-free control of flux densities and precise control of the flux ratio through a calibration technique of reflection high energy electron diffraction (RHEED) oscillations in a molecular beam epitaxial (MBE) system is described. The critical layer thickness for the pseudomorphic growth of InGaAs on InP is found to follow the energy balance model, and a very high two-dimensional electron gas mobility of over 1.5 m/sup 2//Vs and over 15 m/sup 2//Vs at 293 K and 10 K, respectively, is obtained. >

A low frequency noise and charge carriers transport mechanism analysis was performed on tantalum capacitors in order to characterise their quality and reliability. The model ofTa−Ta2O5−MnO2MIS structure was used to give physical interpretation of VA characteristic both in normal and reverse modes. The self-healing process based on the high temperatureMnO2−Mn2O3transformation was studied and its kinetic determined on the basis of noise spectral density changes. The correlation between leakage current and noise spectral density was evaluated and noise reliability indicator was suggested. In normal mode the noise spectral density at rated voltage increases with second power of current and it varies within two decades for given leakage current value. In reverse mode there is only weak correlation and for given applied voltage, the leakage current for all ensemble varies only by one order, whereas the noise spectral density of the same samples spread in five orders.

It has been found that the low‐temperature (

In situ Hall measurements reveal that the mobility of two‐dimensional electron gas 80‐nm‐deep from the surface decreases simultaneously with 10‐keV Ar‐ion irradiation at 90 K. This demonstrates that penetration of irradiation defects far beyond the ion range (projected range =8.8 nm) is due to the channeling effect. Annealing of the irradiated sample was also performed. Partial recovery in the mobility observed indicates that the defects become thermally mobile at above 200 K.

A very high electron mobility pseudomorphic In0.8Ga0.2As heterostructure is successfully grown on InP both by the elimination of the overshoot of flux densities and by the precise control of the flux ratio through a new calibration technique of reflection high‐energy electron diffraction oscillations in a molecular beam epitaxy system. The critical‐layer thickness for the pseudomorphic growth of InGaAs on InP is found to follow the energy balance model, and a very high 2DEG mobility of over 1.5 m2/V s and over 15 m2/V s at 293 and 10 K, respectively, is obtained.

The Hooge parameter of the heavily doped InAs heterostructure decreased monotonically from 2×10−3 at the room temperature down to 5×10−4 at 50K. The dependence of the Hooge parameter of the various high mobility compound semiconductors on the temperature were summarized and interpreted in terms of the scattering mechanisms together with some comments on the absolute values of the Hooge parameter.