Hooge Parameter Research Articles

Low Surface Traps Induced Noise ZrZnO Thin-Film Transistor Using Field-Plate Metal Technology

This study proposes a high-performance top-gate ZrZnO thin-film transistor (TFT) with a novel field-plate (FP) structure. The experimental results show that the Ion/Ioff ratio of the FP TFT is higher than that of a conventional structure. The leakage current and interface traps are reduced simultaneously. The measured low frequency noise spectra also demonstrated that the flicker noise generated by the surface traps can be suppressed by adopting field-plate metal structure for TFT. The field-plate ZrZnO TFT achieved a threshold voltage (VTH) of 0.5 V and the sub-threshold slope (SS) is 0.21 V/decade. In addition, the Ion/Ioff ratio also reached 2.65×104 and the Hooge parameter, αH, is in the range, 10-5 to 10-4 which is a comparatively low trap induced noise range compared to previous studies.

Low-Frequency Electronic Noise in Single-Layer MoS2 Transistors

Ubiquitous low-frequency 1/f noise can be a limiting factor in the performance and application of nanoscale devices. Here, we quantitatively investigate low-frequency electronic noise in single-layer transition metal dichalcogenide MoS2 field-effect transistors. The measured 1/f noise can be explained by an empirical formulation of mobility fluctuations with the Hooge parameter ranging between 0.005 and 2.0 in vacuum (<10(-5) Torr). The field-effect mobility decreased, and the noise amplitude increased by an order of magnitude in ambient conditions, revealing the significant influence of atmospheric adsorbates on charge transport. In addition, single Lorentzian generation-recombination noise was observed to increase by an order of magnitude as the devices were cooled from 300 to 6.5 K.

Interface studies of N2 plasma-treated ZnSnO nanowire transistors using low-frequency noise measurements

Due to the large surface-to-volume ratio of nanowires, the quality of nanowire–insulator interfaces as well as the nanowire surface characteristics significantly influence the electrical characteristics of nanowire transistors (NWTs). To improve the electrical characteristics by doping or post-processing, it is important to evaluate the interface characteristics and stability of NWTs. In this study, we have synthesized ZnSnO (ZTO) nanowires using the chemical vapor deposition method, characterized the composition of ZTO nanowires using x-ray photoelectron spectroscopy, and fabricated ZTO NWTs. We have characterized the current–voltage characteristics and low-frequency noise of ZTO NWTs in order to investigate the effects of interface states on subthreshold slope (SS) and the noise before and after N2 plasma treatments. The as-fabricated device exhibited a SS of 0.29 V/dec and Hooge parameter of ∼1.20 × 10−2. Upon N2 plasma treatment with N2 gas flow rate of 40 sccm (20 sccm), the SS improved to 0.12 V/dec (0.21 V/dec) and the Hooge parameter decreased to ∼4.99 × 10−3 (8.14 × 10−3). The interface trap densities inferred from both SS and low-frequency noise decrease upon plasma treatment, with the highest flow rate yielding the smallest trap density. These results demonstrate that the N2 plasma treatment decreases the interface trap states and defects on ZTO nanowires, thereby enabling the fabrication of high-quality nanowire interfaces.

Possible unified model for the Hooge parameter in inversion-layer-channel metal-oxide-semiconductor field-effect transistors

This paper proposes a possible unified model for the Hooge parameter by considering the impact of transport dimensionality on the Hooge parameter behavior of various inversion-layer-channel metal-oxide-semiconductor field-effect transistors. Past experiments show that the Hooge parameter has a couple of peculiar behaviors. Based on a phenomenological consideration, the original mobility-based model for the Hooge parameter is shown to provide only a partial understanding of the results. It is also observed that, in contrast to past models, the interpretation of some aspects of the Hooge parameter strongly depends on how the two fluctuation modes, the carrier-density fluctuation and the mobility fluctuation, correlate. The phenomenological model proposed here gives a fundamental physical basis that allows important aspects of the Hooge parameter to be interpreted; the model also introduces three basic parameters (the Hooge parameter elements for the carrier-density fluctuation, the mobility fluctuation, and the cross-correlation component). Theoretical expressions for the three basic Hooge parameters are given by merging the fundamental Hooge model, Handel's theory, statistical physics, and quantum-mechanical transport physics. The gate voltage dependence of the Hooge parameter can be explained reasonably well by stating that the screening length rules the dielectric function and that the mobility fluctuation and carrier density fluctuation are correlated. Finally, the theoretical models are examined against the results of past experiments.

Boron-doped nanocrystalline silicon germanium thin films for uncooled infrared bolometer applications

In this paper, boron-doped nanocrystalline Si0.78Ge0.22:H thin film is assessed for use as resistive sensing layer in uncooled infrared bolometer applications. The silicon germanium thin films were deposited by PECVD (plasma enhanced chemical vapor deposition) through decomposition of silane, germane and diborane diluted with argon at substrate temperature of 230°C. Under optimum deposition parameters, the sensing films with modulate electrical resistivity (<104Ωcm) and high temperature coefficient of resistance (TCR) (>−3%/K) were obtained at room temperature. 1/f noise character in the form of the normalized Hooge parameter was measured in the frequency range of 1–64Hz, resulting in a lower 1/f noise compared to other materials currently used for device application.

Role of ${\hbox{HfO}} _{2} $/${\hbox{SiO}}_{2}$ Gate Dielectric on the Reduction of Low-Frequent Noise and the Enhancement of a-IGZO TFT Electrical Performance

High-κ dielectric is regarded as an effective material to reduce the operating voltage of the amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs). However, the dielectric with high permittivity often has the drawbacks of inducing small conduction band offset energy and high interface trap density. Here a bilayer HfO2/SiO2 gate dielectric for thin-film transistors (TFTs) is employed to address the issues. Compare to the a-IGZO TFT with solely 15 nm-thick HfO2 gate dielectric, the TFT with the bilayer HfO2/SiO2 (10 nm/5 nm) gate dielectric improves the subthreshold swing (SS) from 0.22 to 0.12 V/decade, the mobility from 1.4 to 7 cm2/V·s and current on-off ratio from 9×106 to 1.3×10 9. Finally, Hooge's parameters (extracted from the low-frequency noise measurement) of a-IGZO TFTs were investigated to understand the defects near the channel/dielectrics interface so that the role of the thin SiO2 layer can be verified. The device with bilayer HfO2/SiO2 structure exhibits a value of 2×10-3, which is an order of magnitude lower than the one with a single HfO2 layer. The Hooge's parameter of our bilayer dielectric is the lowest among the reported metal-oxide based TFTs on the glass substrate.

Angular Dependence of Low-Frequency Noise in Al$_{2}$O$_{3}$-Based Magnetic Tunnel Junction Sensors With Conetic Alloy

We demonstrated the noise performances of Al2O3-based magnetic tunnel junction sensors (MTJs) in the low-frequency regimes. Conetic alloy Ni77Fe14Cu5Mo4 was deposited as both the MTJ pinned layer and free layer because of its superb magnetically soft properties. A rotating magnetic field was employed to investigate the angular dependence of the MTJ low-frequency noise. Hooge parameter was applied for parameterizing the low-frequency noise. The measurement results demonstrate that the Hooge parameters are angular-dependent and they exhibit a linear relation with respect to the angular magnetoresistive susceptibility. It can be also observed that the Hooge parameters possess a higher value when the Conetic MTJs are in the region of antiparallel state. These results indicate that the magnetic fluctuations in the ferromagnetic layers contribute to the low-frequency noise level in Conetic MTJ sensors.

Correlated Flicker Noise and Hole Mobility Characteristics of $(\hbox{110})/\langle\hbox{110}\rangle$ Uniaxially Strained SiGe FINFETs

Hole mobility and flicker noise characteristics of uniaxially strained <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$( \hbox{110})/\langle\hbox{110}\rangle$</tex></formula> <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Si}_{0.75} \hbox{Ge}_{0.25}$</tex></formula> pFINFETs <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\hbox{SSGOI}_{0.25})$</tex></formula> are investigated in this letter. Equivalent gate referred flicker noise in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{SSGOI}_{0.25}$</tex></formula> is dominated by correlated number and mobility fluctuation in the low-bias regime and Hooge mobility fluctuation in the high-bias regime. The extracted Hooge parameter in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{SSGOI}_{0.25}$</tex></formula> and in Si pFINFETs is <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{10}^{-5}$</tex></formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{10}^{-4}$</tex></formula> , respectively. The lower value of the Hooge parameter in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{SSGOI}_{0.25}$</tex></formula> pFINFETs is attributed to improved phonon-limited mobility compared to the SOI pFINFETs. <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{SSGOI}_{0.25}\ \hbox{FINFETs}$</tex></formula> are found to exhibit the lowest equivalent gate referred flicker noise among any nonplanar devices reported to date.

Field sensing in MgO double barrier magnetic tunnel junctions with a superparamagnetic Co50Fe50 free layer

Linear response and low frequency noise have been investigated in MgO double barrier magnetic tunnel junctions with a superparamagnetic Co50Fe50 free layer. Linear and hysteresis-free switching was observed for the Co50Fe50 thickness t ≤ 1 nm. A tunneling magnetoresistance ratio of up to 108% and large magnetic field sensitivity value of 61%/mT were obtained at room temperature when t = 1.0 nm. The angular dependence of magnetoresistance suggests that weak coupling between superparamagnetic islands in a 1.0 nm free layer permits continuous rotation of magnetization, whereas the islands in a 0.8 nm layer switch rather independently. The frequency dependence of noise power spectrum density and field dependence of Hooge parameter (α) also behave differently for junctions with 0.8 and 1.0 nm free layers. The noise sensitivity of 1.0 nm free layer junctions is independent of bias, and it is estimated to reach 400 pT/Hz0.5 at 500 kHz.

Epitaxial La0.7Sr0.3MnO3 thin films grown on SrTiO3 buffered silicon substrates by reactive molecular‐beam epitaxy

AbstractLa0.7Sr0.3MnO3 (LSMO) thin films (with a thickness of 10, 20, 60, 75, and 100 nm) were grown on SrTiO3 (STO)‐buffered silicon (001) substrates by reactive molecular‐beam epitaxy. X‐ray diffraction (XRD) revealed the heterostructures to be fully epitaxial with orientation relationship (001) LSMO || (001) STO || (001) Si and [100] LSMO || [100] STO || [110] Si. Root mean square roughness was about 0.5 nm as measured by atomic force microscopy (AFM) for films of 10–75 nm thicknesses, and about 1 nm for the 100 nm thick LSMO film. Normalized Hooge parameters in the (0.95 ± 0.25) × 10−30–(3.41 ± 0.71) × 10−30 m3 range were measured at 300 K, which are comparable to the noise level typically measured in the best LSMO films on (001) STO substrates. Overall these very low noise LSMO films with thicknesses in the 10–100 nm range grown on STO/Si showed properties rivaling those of LSMO films deposited on (001) STO single crystal substrates, thus demonstrating their potential use for LSMO‐based devices on silicon substrates.

Study of RF Reliability of GaN HEMTs Using Low-Frequency Noise Spectroscopy

The results of continuous wave short-term RF stress applied at 3 GHz on GaN high electron mobility transistors on silicon substrate are presented. The degradation of the device characteristics for RF overdrive conditions from 3-dB to 8-dB gain saturation is discussed. Output RF power degrades significantly in a short period of time. Both transient and permanent degradation of electronic properties of the device are identified. After high RF gain compression levels, DC characteristics like the threshold voltage and gate leakage current change permanently. Detailed microscopic changes in the electronic structure of the device were studied by performing simultaneous low-frequency noise measurements of gate and drain currents before and after stress. The channel was found to be immune to the whole stress regime with no increase of the Hooge parameter. On the other hand, activation of unstable defects and then an increase of the defect density near the gate metal semiconductor interface were observed from gate noise measurements. A point defect located at around 4.5 nm from the gate metal semiconductor interface with activation energy of 0.9 eV below the AlGaN conduction band edge was determined from random telegraph noise measurements. The role of forward gate biasing as a failure mechanism is also discussed.

Mobility-Dependent Low-Frequency Noise in Graphene Field-Effect Transistors

We have investigated the low-frequency 1/f noise of both suspended and on-substrate graphene field-effect transistors and its dependence on gate voltage, in the temperature range between 300 and 30 K. We have found that the noise amplitude away from the Dirac point can be described by a generalized Hooge's relation in which the Hooge parameter α(H) is not constant but decreases monotonically with the device's mobility, with a universal dependence that is sample and temperature independent. The value of α(H) is also affected by the dynamics of disorder, which is not reflected in the DC transport characteristics and varies with sample and temperature. We attribute the diverse behavior of gate voltage dependence of the noise amplitude to the relative contributions from various scattering mechanisms, and to potential fluctuations near the Dirac point caused by charge carrier inhomogeneity. The higher carrier mobility of suspended graphene devices accounts for values of 1/f noise significantly lower than those observed in on-substrate graphene devices and most traditional electronic materials.

Low-frequency noise in planar Hall effect bridge sensors

The low-frequency characteristics of planar Hall effect bridge sensors are investigated as function of the sensor bias current and the applied magnetic field. The noise spectra reveal a Johnson-like spectrum at high frequencies, and a 1/ f-like excess noise spectrum at lower frequencies, with a knee frequency of around 400 Hz. The 1/ f-like excess noise can be described by the phenomenological Hooge equation with a Hooge parameter of γ H = 0.016. The detectivity is shown to depend on the total length, width and thickness of the bridge branches. The detectivity is improved by the square root of the length increase. Moreover, the detectivity is shown to depend on the amplitude of the applied magnetic field, revealing a magnetic origin to part of the 1/ f noise.

Barrier height dependence of Fano factor and 1/f noise effect on InGaP based Schottky barrier diode

We report a study on flicker noise reduction in the space charge limitation region of a Zn-Pd/n-In0.49Ga0.51P Schottky barrier diode (SBD). A suitable model has been suggested to explain the barrier height dependence of the Fano factor. The reduction of Fano factor with barrier height has been experimentally investigated from I-V characteristics and noise power density measurements. Finally a comparative study was made with the theoretically obtained value of the Fano factor. Another important parameter, known as the Hooge parameter, of InGaP SBD has also been calculated as a function of temperature.

Annealing effect on low frequency noise in MgO-based magnetic tunnel junctions

The annealing temperature (Ta) dependence of the low frequency noise in exchange-biased magnetic tunnel junctions (MTJs) with an MgO barrier and CoFeB electrodes has been investigated for 200 < Ta < 425 °C. A 1/f noise spectrum is observed for the parallel and antiparallel states, where the Hooge parameter (α) for the parallel state remains unchanged with Ta after the CoFeB electrodes is fully crystallized, while α for the antiparallel state increases over the range of Ta from 275 to 425 °C. The 1/f noise for the antiparallel state is largely of magnetic origin, and it can be attributed to magnetization fluctuations of ferromagnetic electrodes due to the loss of the exchange bias, whereas there is little magnetic noise in the parallel state. An annealing temperature of 325 °C yields an optimized signal-to-noise ratio, as the CoFeB electrodes become fully crystallized. The bias dependence of α is discussed based on the Glazman-Matveev model, which considers both elastic and inelastic tunneling.

Investigation of Stress Memorization Process on Low-Frequency Noise Performance for Strained Si n-Type Metal–Oxide–Semiconductor Field-Effect Transistors

The use of low-frequency (1/f) noise to evaluate low-cost stress-memorization technique (SMT) induced-stress in n-type metal–oxide–semiconductor field-effect transistors has been investigated. As compared to device without SMT process, the comparable 1/f noise level obtained for strained Si devices with the low-cost SMT process indicates that adding the low-cost SMT process will not affect the Si/SiO2 interface quality. Moreover, through observing experiment result and Hooge's parameter αH, the mechanism of 1/f noise in the both devices can be properly interpreted by the carrier number fluctuations correlated mobility fluctuations (unified model).

Direct current effects on 1/f noise in patterned Permalloy films

Detailed investigations of 1/f noise were performed in patterned Permalloy films. The gold bridges for the four probe measurement setup were deposited on a quartz substrate. Pattern geometry, bias current, and transverse magnetostatic field effects on the material’s 1/f noise were studied. The normalized Hooge parameter and frequency slope were analyzed in the framework of the empirical Hooge relation. Different dependences of the noise versus bias current generated Oersted field and the magnetostatic field were observed. The normalized Hooge parameter and frequency slope were pattern width and field configuration dependent.

Magnetic Tunnel Junction Sensors With Conetic Alloy

Al2O3 magnetic tunneling junction (MTJ) sensors were fabricated with Conetic alloy Ni77Fe14Cu5Mo4 deposited as the free layer and pinned layer for its soft magnetic properties. It was observed that the Al2O3 MTJ sensors with Conetic exhibited relatively small easy-axis coercivity. Tunneling magnetoresistance (TMR) and noise measurements were carried out to characterize the sensors. TMR of 9.5% and Hooge parameter of 3.825 × 10-7 μm2 were achieved without any hard-axis field. Hard-axis bias field was applied to eliminate the hysteresis and improve the linear field response of the MTJ sensor. The hysteresis was removed by applying an external magnetic field along the hard axis at 8 Oe and the sensor sensitivity was 0.4 %/Oe within a linear region at room temperature. The relationship between the Hooge parameter and hard-axis field was also investigated and the result demonstrated that the 1/f noise can be suppressed by an optimized hard-axis bias field. This work shows that it is feasible to use Conetic alloy as the soft magnetic layers in MTJ sensors for its small coercivity, and a hard-axis bias field can be used to linearize the sensor response and suppress the 1/f noise.

LOW-FREQUENCY ELECTRONIC NOISE IN GRAPHENE TRANSISTORS: COMPARISON WITH CARBON NANOTUBES

We report results of the experimental investigation of the low-frequency noise in graphene transistors. The graphene devices were measured in three-terminal configuration. The measurements revealed low flicker noise levels with the normalized noise spectral density close to 1/f (f is the frequency) and the Hooge parameter αH ~10-3. Both top-gate and back-gate devices were studied. The analysis of the noise spectral-density dependence on the gate biases helped us to elucidate the noise sources in these devices. We compared the noise performance of graphene devices with that of carbon nanotube devices. It was determined that graphene devices works better than carbon nanotube devices in terms of the low-frequency noise. The obtained results are important for graphene electronic, communication and sensor applications.

Diagnosis of low-frequency noise sources in contact resistance of staggered organic transistors

A diagnostic procedure for the contact low-frequency noise sources of staggered organic transistors is presented. Like the conventional process for channel noise, the two models of carrier number fluctuations and Hooge mobility fluctuations are concerned. Both models apply to bis(triisopropylsilylethynyl) pentacene transistors at lower and higher current densities, where the contact defect density is 1000 times higher than that in the channel and a Hooge parameter around 1 is obtained, respectively. The Hooge mobility fluctuations model well accounts for the contact noise in pentacene transistors with a Hooge parameter in the range of 0.5–3.