Low-frequency Noise Measurements Research Articles

Dispersion study of DC and Low Frequency Noise in SiGe:C Heterojunction Bipolar Transistors used for mm-Wave to Terahertz applications

This work presents an investigation of DC and Low Frequency Noise dispersion in 0.13μm SiGe:C BiCMOS Heterojunction Bipolar Transistors (HBTs) used for mm-Wave to Terahertz applications. Therefore, DC and Low Frequency Noise measurements have been performed over a half wafer on a large number of transistors. A statistical 1/f noise compact model is presented as well as a study of the repartition of generation-recombination components. The main Low Frequency Noise sources are found to be homogenously distributed in the intrinsic base-emitter junction. The mean 1/f noise level, evaluated by the figure of merit KBmean, is equal to 6 10−10μm2.

Electrical Characteristics of Multilayer MoS2 Transistors at Real Operating Temperatures and Different Ambient Conditions

We describes the electrical characteristics of multilayer MoS2 thin film transistors (TFTs) through variable temperature measurement (from room temperature up to 350 K) and different operating ambients (in air and in a vacuum, ~10-5 Torr). Carrier transport mechanism was predicted through the observed temperature dependent electrical parameters (threshold voltage, field effect mobility, sub-threshold slope). Preliminary evidences were explained that the dominant transport mechanism of multilayer MoS2 TFTs could be the combination of the optical phonon scattering and thermionic emission depending on the working temperature. Furthermore, through additional low-frequency noise measurement, we supported the expectation that the multilayer MoS2 has better immunity than single-layer for the effect of chemisorption because multilayer MoS2 has relativley thick compared to Debye length where real carrier transportation occurs in the underlying channel.

High Temperature Performance of MoS2 Thin Film Transistors

We report on the characteristics of long channel (1 to 2 micron MoS2 thin film transistors) measured in the temperature range from 25 oC to 200 oC. Using the long channel allowed us minimizing the effect of the contact resistance for a more accurate extraction of the effective field effect mobility in the channel. The extracted field effect mobility, see Fig.1, (varying from 5 to 7 cm2/V-s in different samples) was only a very weak function of temperature. The on-to-off ratio was ~ 104 at room temperature decreasing to 103 at 220 oC. The devices had the threshold voltage varying from 80 V to 40 V when temperature increased from 25 oC to 220 oC, see Fig. 2. A very large subthreshold slope of nearly 11 V corresponded to the density of states in the energy gap of approximately 3x1013 cm-2 or approximately 3 x1012 1/(eVcm2) at the band edge. The low frequency noise measurements in the range from 1 Hz to 100 Hz revealed 1/f noise with no recombination-generation bulges. The density of traps extracted from the noise data using the McWhorter model was close to that extracted from the temperature measurement. Our results show that MoS2 TFTs can compete with a-Si TFTs and a-Si sensors for high temperature applications.

A Novel Method for Reliability Estimation of Optoelectronic Coupled Devices Based on Low-frequency Noise Measurements

In this paper the theoretical analysis of Low-frequency (LF) noise sources in Optoelectronic Coupled Devices (OCDs) is given and the relation between typical defects and LF noise (1/f noise, generationrecombination (g-r) nosie and burst noise) is described. According to LF noise sources of OCDs and device reliability estimation methods, a novel measurement system based on virtual instrument for OCDs is introduced and nV-level measurement precision can be achieved with the typical LF noise measurement system, which can be used to screen potential devices with excess noise and assess device relibility classifications. In this experiment, the top and bottom limitative thresholds were used to estimate the components parameters of the Power Spectrum Density (PSD) for estimating the reliability of OCDs by the average noise PSD for the 200 OCDs and the classification criterions of electronic components. The experimental results demonstrated that high reliability requirements can be satisfied.

Growth of highly textured SnS on mica using an SnSe buffer layer

We report the growth of SnS thin films on mica substrates by molecular beam epitaxy. Excellent 2D layered structure and strong (001) texture were observed with a record low rocking curve full width at half maximum of ~0.101° for the SnS(004) diffraction. An interface model is used to investigate the nucleation of SnS on mica which indicates the co-existence of six pairs of lateral growth orientations and is in excellent agreement with the experimental Φ-scan measurements indicating 12 peaks separated by 30° from each other. To control the lateral growth of the SnS epilayers we investigate the utilization of a thin SnSe buffer layer deposited on the mica substrate prior to the growth of the SnS thin film. The excellent lattice match between SnSe and mica enhances the alignment of the nucleation of SnS and suppresses the minor lateral orientations along the mica[110] direction and its orthogonal axis. Detailed low-frequency noise measurement was performed to characterize the trap density in the films and our results clearly demonstrate substantial reduction in the density of the localized states in the SnS epilayer with the use of an SnSe buffer layer.

Low Phase Noise GaN HEMT Oscillators With Excellent Figures of Merit

This letter presents guidelines for the design of low phase noise oscillators in GaN high electron mobility transistor (HEMT) technology. The design starts from bias-dependent low-frequency (LF) noise measurements. Oscillator topology and bias point are then chosen for operation in regions where LF noise is low. The best LF noise properties are obtained for low drain voltage and current. Thus, the low phase noise can be achieved at low dc power which also means that power normalized phase noise figure of merit (FOM) will be good.

High Breakdown Voltage and Low Thermal Effect Micromachined AlGaN/GaN HEMTs

This work develops a thermally stable micromachined AlGaN/GaN high-electron mobility transistor (HEMT) with an enhanced breakdown voltage. After removal of the Si substrate beneath the HEMT, a 300-nm SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and a 20-μm copper layer are deposited to form the GaN-on-insulator (G.O.I.) structure. The self-heating at high current that is exhibited by GaN HEMTs that are by previously developed full substrate removal methods is eliminated. The need for complicated substrate-transfer technology is also eliminated, increasing chip package yield. The low frequency noise measurement results also demonstrate that the trap density of the buffer/transition layer is reduced by the removal of the substrate and micromachining of the HEMTs.

Mobility Degradation Effect to Hooge's Constant in Recessed-Gate &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;${\rm Al}_{2}{\rm O}_{3}/{\rm AlGaN}/{\rm GaN}$ &lt;/tex-math&gt;&lt;/inline-formula&gt; MIS Power Transistors

We investigated the low-frequency noise (LFN) characteristics of recessed-gate Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /AlGaN/GaN MIS power transistors. Compared with normally ON devices, the gate-recess processes are only added in normally OFF devices. The extracted threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) values of the normally ON and normally OFF devices are -7 and 4 V, respectively. However, the normally OFF devices additionally suffer from mobility degradation. Furthermore, the Hooge's constant (α <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> ) of the normally OFF devices is ~15 times higher than that of the normally ON devices. From the LFN measurement results, the main cause for this significant difference is the mobility fluctuation due to impurity scattering in the recessed-gate devices.

Low-frequency noise assessment in advanced UTBOX SOI nMOSFETs with different gate dielectrics

In this paper, UTBOX nMOSFETs with different gate dielectrics have been studied based on their low-frequency noise (LFN) performance. Since LFN measurements have been successfully used as a characterization tool for determining the quality of the films, here, we have investigated the dielectric films used in state-of-the-art UTBOX devices in order to evaluate their performance and to identify the type of traps possibly introduced during the device processing.High-k gate dielectric devices have shown predominantly 1/f noise with a two-order of magnitude higher value than the conventional SiO2 ones which, consequently, results in higher density of traps in those devices. The carrier number fluctuations dominate the 1/f noise for both front and back interfaces. Due to the thin silicon film thickness there is a strong electrostatic coupling between front and back interfaces that interferes in the noise results as well as in transistor parameters. A contribution of the back interface noise source of about 14% on the measured noise in the front channel conduction was found, while the contribution of the front interface noise source is about 22% on the measured noise in the back channel conduction.The generation–recombination (GR) noise performed at different temperatures has enabled the identification of 6 types of traps and 2 unknown ones, being originated from the dry-etching or implantation damage.

In depth static and low-frequency noise characterization of n-channel FinFETs on SOI substrates at cryogenic temperature

The impact of cryogenic temperature operation (10K) on the short channel effects and low frequency noise was analysed on strained and unstrained n-channel FinFET transistors fabricated on silicon on insulator (SOI) substrates in order to evaluate the devices static performances and to study the low frequency noise mechanisms. The main electrical parameters are investigated and it is evidenced that even at very low temperatures, the strain-engineering techniques boost the devices performances in terms of mobility, threshold voltage, access resistances and drain saturation currents. The DIBL effect, Early voltage and the intrinsic gain are ameliorated only for the short channel devices. A drawback, however, is that slightly improved turn-on capabilities may be noted for standard channel devices compared to strained ones. Low frequency noise measurements show that the carrier number fluctuations dominate the flicker noise in weak inversion even at 10K operation. Access resistance noise contributions were evidenced in strong inversion.

Low-frequency 1/f noise in MoS2 transistors: Relative contributions of the channel and contacts

We report on the results of the low-frequency (1/f, where f is frequency) noise measurements in MoS2 field-effect transistors revealing the relative contributions of the MoS2 channel and Ti/Au contacts to the overall noise level. The investigation of the 1/f noise was performed for both as fabricated and aged transistors. It was established that the McWhorter model of the carrier number fluctuations describes well the 1/f noise in MoS2 transistors, in contrast to what is observed in graphene devices. The trap densities extracted from the 1/f noise data for MoS2 transistors, are 2 × 1019 eV−1cm−3 and 2.5 × 1020 eV−1cm−3 for the as fabricated and aged devices, respectively. It was found that the increase in the noise level of the aged MoS2 transistors is due to the channel rather than the contact degradation. The obtained results are important for the proposed electronic applications of MoS2 and other van der Waals materials.

A very low noise, high accuracy, programmable voltage source for low frequency noise measurements.

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level.

Field-induced macroscopic barrier model for persistent photoconductivity in nanocrystalline oxide thin-film transistors

Persistent photoconductivity (PPC) in nanocrystalline InZnO thin-film transistors (TFTs) was studied using carrier fluctuation measurements and transient analysis. Low-frequency noise measurements and decay kinetics indicate that the band bending by the external field together with the ionized oxygen vacancy (Vo++) generated during the light exposure is the main cause of the PPC phenomenon. Based on these observations, a field-induced macroscopic barrier model is proposed as the origin of PPC for InZnO TFTs. In particular, this model explains that the carrier separation between e and Vo++ is induced by the external field applied to the three electrodes inside the transistor.

Electrical transport and low-frequency noise in chemical vapor deposited single-layer MoS2 devices

We have studied temperature-dependent (77–300 K) electrical characteristics and low-frequency noise (LFN) in chemical vapor deposited (CVD) single-layer molybdenum disulfide (MoS2) based back-gated field-effect transistors (FETs). Electrical characterization and LFN measurements were conducted on MoS2 FETs with Al2O3 top-surface passivation. We also studied the effect of top-surface passivation etching on the electrical characteristics of the device. Significant decrease in channel current and transconductance was observed in these devices after the Al2O3 passivation etching. For passivated devices, the two-terminal resistance variation with temperature showed a good fit to the activation energy model, whereas for the etched devices the trend indicated a hopping transport mechanism. A significant increase in the normalized drain current noise power spectral density (PSD) was observed after the etching of the top passivation layer. The observed channel current noise was explained using a standard unified model incorporating carrier number fluctuation and correlated surface mobility fluctuation mechanisms. Detailed analysis of the gate-referred noise voltage PSD indicated the presence of different trapping states in passivated devices when compared to the etched devices. Etched devices showed weak temperature dependence of the channel current noise, whereas passivated devices exhibited near-linear temperature dependence.

Experimental characterization of low-frequency noise in power MOSFETs for defectiveness modelling and technology assessment

In this work we analyse the applicability of low-frequency (LF) noise measurement in order to study the defectiveness in the gate oxide of power MOSFETs (Metal–Oxide–Semiconductor Field-Effect Transistors). To this purpose, we implement a low-noise experimental set-up, which is able to measure, in particular, the flicker (“1/f”) contribution to the drain noise current of the device under test, with high accuracy in terms of noise floor and the adequate bias system flexibility required by the application. First, we show how these measurements can be used to empirically detect the physical model and related compact expressions, which best describe the source of 1/f-like fluctuations in this type of devices. Then, according to the selected physical model, the defect density in the gate oxide is extracted. In order to validate the proposed methodology, experimental data are reported and discussed in the case of power U-MOSFETs.

Low Frequency Noise and It's Psychological Effects

Objective: This entire study has two parts. Study I aimed to develop a psychological assessment scale and the study II aimed to investigate the effects of LFN (low frequency noise) on the psychological responses in humans, using the scale developed in the study I.<BR><BR> Background: LFN is known to have a negative impact on the functioning of humans. The negative impact of LFN can be categorized into two major areas of functioning of humans, physiological and psychological areas of functioning. The physiological impact can cause abnormalities in threshold, balancing and/or vestibular system, cardiovascular system and, hormone changes. Psychological functioning includes cognition, communication, mental health, and annoyance.<BR><BR> Method: 182 college students participated in the study I in development of a psychological assessment scale and 42 paid volunteers participated in the study II to measure psychological responses. The LFN stimuli consisted of 12 different pure tones and 12 different 1 octave-band white noises and each stimulus had 4 different frequencies and 3 different sounds pressure levels.<BR><BR> Results: We developed the psychological assessment scale consisting of 17 items with 3 dimensions of psychological responses (i.e., perceived physical, perceived physiological, and emotional responses). The main findings of LFN on the responses were as follows: 1. Perceived psychological responses showed a linear relation with SPL (sound pressure level), that is the higher the SPL is, the higher the negative psychological responses were. 2. Psychological responses showed quadric relations with SPL in general. 3. More negative responses at 31.5Hz LFN than those of 63 and 125Hz were reported, which is deemed to be caused by perceived vibration by 31.5Hz. "Perceived vibration" at 31.5Hz than those of other frequencies of LFN is deemed to have amplified the negative psychological response. Consequently there found different effects of low frequency noise with different frequencies and intensity (SPL) on multiple psychological responses.<BR><BR> Conclusion: Three dimensions of psychological responses drawn in regard to this study differed from others in the frequencies and SLP of LFN. Negative psychological responses are deemed to be differently affected by the frequency, SPL of the LFN and "feel vibration" induced by the LFN.<BR><BR> Application: The psychological scale from our study can be applied in quantitative psychological measurement of LFN at home or industrial environment. In addition, it can also help design systems to block LFN to provide optimal conditions if used the study outcome, .i.e., the relations between physical and psychological responses of LFN.

Low-frequency noise in diagnostics of power blue InGaN/GaN LEDs

Low-frequency noise measurements, combined with the conventional techniques for the study of InGaN/GaN-based LEDs, make it possible to separate the contribution of conductive paths associated with the extended defect system (EDS) and point defects (PD) to non-radiative recombination processes. These measurements also can reveal physical mechanisms leading to the unpredictable failure of LEDs, such as non-uniform current distribution, local overheating, and presence of local InGaN regions with a reduced band gap width Eg.

Characterization and Modeling of the Conduction and Switching Mechanisms of HfOx Based RRAM

ABSTRACTThe conduction and switching mechanism of resistive random access memory (RRAM) is reviewed in this paper. The resistive switching in oxides is generally attributed to the conductive filament (made up of oxygen vacancies) formation and rupture in the oxide due to field assisted oxygen ion migration. As a model system for device physics study, HfOx based RRAM devices were fabricated and characterized. To identify the electron conduction mechanism, various electrical characterization techniques such as I-V measurements at various temperatures, low-frequency noise measurements, and AC conductance measurements were employed. It was suggested that the trap-assisted-tunneling is the dominant conduction mechanism. In order to explore the oxygen ion migration dynamics, pulse switching measurements were performed. An exponential voltage-time relationship was found between the switching time and the applied voltage. To obtain a first-order understanding of the variability of resistive switching, a Kinetic Monte Carlo (KMC) numerical simulator was developed. The generation/recombination/migration probabilities of oxygen vacancies and oxygen ions were calculated, and the conductive filament configuration was updated stochastically according to those probabilities. The KMC simulation can reproduce many experimental observations in the DC I-V sweep, pulse switching, endurance cycling, and retention baking, etc. The tail bits in the resistance distribution are attributed to the oxygen vacancy left over in the gap region due to a competition between the oxygen vacancy generation and recombination. To enable circuit and system development using RRAM, a compact device model was developed. The compact model, implemented in MATLAB, HSPICE, and Verilog-A, which can be employed in many commonly available circuit simulators using the SPICE engine.

Proton-Induced Dehydrogenation of Defects in AlGaN/GaN HEMTs

The responses to 1.8 MeV proton irradiation of AlGaN/GaN HEMTs grown under Ga-rich and ammonia-rich conditions are investigated in this work. Changes in defect energy distributions of AlGaN/GaN HEMTs during proton irradiation are characterized via temperature-dependent low-frequency noise measurements. Density functional theory calculations show these changes are consistent with the reconfiguration and/or dehydrogenation of oxygen-related defects in Ga-rich devices.

Characterization of High-Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors by Low-Frequency Noise Measurements

The instability of amorphous InGaZnO thin-film transistors is investigated under high drain current stress by applying bias voltages to both gate and drain electrodes. The instability involves positive threshold voltage shift, reduction of the ON-state current and recovery of the transfer characteristic toward the prestressed state when the stressed device is unbiased in dark at room temperature for an extended period. This instability behavior is investigated by low-frequency noise measurements before and after stress in the forward and reverse configurations. The overall results are consistent with the instability mechanism involving electron trapping in the existing donor-like gate oxide trap states near the source side.