Kink Effect Research Articles

Temperature influence on experimental analog behavior of MISHEMTs

This work presents an analysis on experimental analog behavior of MISHEMTs operating in the temperature range from 450 K down to 200 K. The drain current (IDS) presented a slight anomaly, especially for temperatures lower than 400 K. In the transconductance it is possible to visualize a second peak, suggesting a second conduction. As shown, the transconductance presented a low dependence on gate length, and an anomaly was observed for the devices at 350 K. The output conductance and transistor efficiency behavior suggest a competition between the effects of the MOS and HEMT conductions, present in the device. A new kink was observed in the output characteristic (IDSxVDS) at room temperature, which is caused by the HEMT and MOS conductions interaction, and it is even more noticeable for higher overdrive voltages (VGT). This effect is called MISHEMT kink effect (MH-kink) in this work. The MH-kink shifts toward higher VDS for higher overdrive voltage, showing the stronger influence of the MOS conduction on the total drain current. The unity gain frequency (ft) increases from 800 MHz (450 K) to 1.8 GHz (200 K), while the AV goes in opposite direction from 43 dB (450 K) to 38 dB (200 K). Considering that the intrinsic voltage gain is good enough even at low temperatures, the MISHEMT can be identified as a good candidate for analog applications.

Understanding the Role of Surface Chemistry in Nanocellulose Kink Formation: A Case Study of TEMPO-Mediated Oxidation.

This study found that the sources of cellulose have a significant effect on the parameters related to the kinks present in nanocellulose. During nanocellulose preparation, 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation induced partial depolymerization on whole cellulose and made the amorphous regions more susceptible to consequent mechanical treatment irrespective of cellulose sources. However, plant cellulose microfibrils were prone to break into shorter nanocellulose with fewer kinks, while bacterial and tunicate cellulose were more likely to bend rather than break, thus leading to the generation of more kinks. The kinks did not show significant effects on the size, crystallinity index, and thermal properties of nanocellulose for each cellulose source, though the kink numbers were positively related to the mechanical performance of nanocellulose. Collectively, this study elucidated the kink formation mechanisms and clarified the effects of kinks on nanocellulose performance, thus providing new insights into understanding the source and behaviors of microdefects present in nanocellulose.

A Conclusive Algorithm with Kink Effects for Fitting 3-D FinFET and Planar MOSFET Characteristic Curves

A Conclusive Algorithm with Kink Effects for Fitting 3-D FinFET and Planar MOSFET Characteristic Curves

Current Kink Effect in β-Ga₂O₃ MOSFETs Induced by Incomplete Ionization of Donors

Current Kink Effect in <i>β</i>-Ga₂O₃ MOSFETs Induced by Incomplete Ionization of Donors

Kink effect on the lattice properties of one-dimensional carbyne nanocrystals under high temperature

Carbyne nanocrystal (CN), as a kind of one-dimensional (1D) sp-hybridized carbon allotrope, has attracted much attention due to its excellent optical and transport properties. However, the lattice properties of 1D CNs under high temperature remain unclear. In our work, we investigate the stability and lattice properties of 1DCNs based on the atomic-bond-relaxation (ABR) approach and first-principles calculations. We find the change of transverse vibration frequencies and bond kinks induced by the thermal effect plays a significant role in the mechanical properties of 1D CNs. We establish a relationship between kink angle and phonon vibration modes, giving a deep inside into high frequency and low-frequency vibration behavior of 1D CNs. Our results indicate the phonon vibration modes modulated by kinks under applied temperatures can lead to a negative thermal expansion behavior in the axial direction of 1D CNs, suggesting an effective way to control the thermal properties of 1D CNs for practical applications.

Kink of the nuclear charge radius isotope shift and overlaps of the neutron and proton orbitals in lead

Within the relativistic mean field approximation, we analyse the kink effect (KE) in the evolution of the charge radius isotope shift of lead isotopes as a function of the neutron number N. We show that if the interactions between neutron and proton states responsible for the KE are assumed to be proportional either to the overlaps of their corresponding wave functions or to those of their corresponding probability density distributions, it is not possible, by themselves, to explain the KE. However, we find that the small component of the single-particle Dirac spinors plays a relevant role in the kink formation. By considering the contribution of the N−126 valence neutrons to the proton central potential, we can explain the generation of the KE and why neutrons in the 1i11/2 orbital are more kinky than when they are in the 2g9/2 orbital.

A note on the covariate-dependent kink threshold regression model for panel data

This article provides new estimating and testing procedures for the panel covariate-dependent kink threshold regression model. By utilizing a linearization technique, we develop an efficient estimator that offers a computationally viable alternative to the grid-search approach. Then we propose a novel testing procedure based on the score statistic to examine the existence of the covariate-dependent kink effect. The test statistic only requires fitting the model in the absence of varying kink threshold, greatly reducing computing time. Extensive simulation studies demonstrate that the proposed method outperforms existing methodologies. To further illustrate their performance, we utilize a real-data analysis. The results demonstrate the practicality and effectiveness of our approach in a wide range of scenarios.

Temperature Nonmonotonic Behavior of GaN HEMTs Kink Effect Caused by Trap-Assisted Impact Ionization

Temperature Nonmonotonic Behavior of GaN HEMTs Kink Effect Caused by Trap-Assisted Impact Ionization

Origin and suppression of kink effect in InP high electron mobility transistors at cryogenic temperatures

The kink effect is a phenomenon that typically occurs in InP-based InAlAs/InGaAs high electron mobility transistors (HEMTs) at cryogenic temperatures. It results in higher output conductance (gDS) and non-monotonic behavior. This Letter discusses the origin and suppression of the kink effect in InP HEMTs at cryogenic temperatures, which is linked to the structure of gate recess passivation. At room temperature, two devices with different gate recess passivation structures show similar characteristics. However, a temperature-sensitive kink is observed in the non-passivated gate recess structure, leading to the discontinuous transconductance (gm) and the non-monotonic threshold voltage (Vth) shifts. Based on pulsed and static (non-pulsed) measurement data, surface traps and impact ionization in the high-field region are identified as the origin of the kink effect. Specifically, a positive Vth shift of +160 mV is caused by surface traps when the temperature drops to 150 K. A negative Vth shift of –60 mV is due to the enhanced impact ionization below 150 K. Conversely, the device with a passivated gate recess has a negligible kink effect and effectively improves discontinuous gm and the non-monotonic Vth shifts (+25 mV) when the temperature drops. Therefore, the device with a passivated gate recess is significant for suppressing the kink effect and maintaining the stability of the device in variable temperature environments.

Estimation and inference for multi-kink expectile regression with nonignorable dropout

In this paper, we consider parameter estimation, kink points testing and statistical inference for a longitudinal multi-kink expectile regression model with nonignorable dropout. In order to accommodate both within-subject correlations and nonignorable dropout, the bias-corrected generalized estimating equations are constructed by combining the inverse probability weighting and quadratic inference function approaches. The estimators for the kink locations and regression coefficients are obtained by using the generalized method of moments. A selection procedure based on a modified BIC is applied to estimate the number of kink points. We theoretically demonstrate the number selection consistency of kink points and the asymptotic normality of all estimators. A weighted cumulative sum type statistic is proposed to test the existence of kink effects at a given expectile, and its limiting distributions are derived under both the null and the local alternative hypotheses. Simulation studies show that the proposed estimators and test have desirable finite sample performance in both homoscedastic and heteroscedastic errors. An application to the Nation Growth, Lung and Health Study dataset is also presented.

Adaptation and comparative analysis of HSPICE level‐61 and level‐62 model for a‐IGZO thin film transistors

AbstractThis paper presents a Computer‐aided design (CAD) model for a‐IGZO thin film transistors (TFTs) by adapting SPICE level‐61 RPI a‐Si: H (Hydrogenated Amorphous Silicon) TFT model and level‐62 RPI Poly‐Si (Poly Silicon) TFT model. This work provides a complete understanding of SPICE level‐61 and 62 model parameters, which must be tuned for a‐IGZO TFT simulation. The adapted SPICE models of level‐61 and level‐62 could model all regions of operation of the TFT, that is, above‐threshold and below‐threshold regions. Adapted RPI poly‐Si model also shows the kink effect in ZnO thin film transistors (TFTs) due to the recombination of electron–hole pairs in the channel via boundary trap states present in the poly‐Si TFTs thereby increasing the drain current in the transistors above pinch‐off region. The extracted performance parameters of the adapted models were found to be contiguous with experimental results. The maximum deviation in the subthreshold slope is approximately 5 mV/decade for level‐61 a‐Si TFT, and for level‐62 poly‐Si TFT, deviation in the subthreshold slope is even less, that is, 0.2 mV/decade. The experimental and simulated characteristics, extracted on‐to‐off ratio, negative bias reverse saturation current, and threshold voltage were almost similar. However, an average deviation of 2.4% and 2.27% was observed in the output characteristics of the adapted level‐61 and level‐62 models, respectively.

Scalable Large-Signal Modeling for GaN HEMTs Including Kink Effect

Scalable Large-Signal Modeling for GaN HEMTs Including Kink Effect

Subthreshold Kink Effect in Gate-All-Around MOSFETs Based on Void Embedded Silicon on Insulator Technology

Subthreshold Kink Effect in Gate-All-Around MOSFETs Based on Void Embedded Silicon on Insulator Technology

Accurate Modeling of GaN HEMTs Oriented to Analysis of Kink Effects in S22 and h21: An Effective Machine Learning Approach

Accurate Modeling of GaN HEMTs Oriented to Analysis of Kink Effects in S₂₂ and h₂₁: An Effective Machine Learning Approach

Conclusive Model-Fit Current–Voltage Characteristic Curves with Kink Effects

Current–voltage characteristic curves of NFinFET are presented and fitted with modified current–voltage (I-V) formulas, where the modified term in the triode region is demonstrated to be indispensable. In the as-known I-V formula, important parameters need to be determined to make both the measured data and the fitting data as close as possible. These parameters include kN (associated with the sizes of the transistor and mobility), λ (associated with early voltage), and Vth (the threshold voltage). The differences between the measured data and the fitting data vary with the applied source–drain bias, proving that the mobility of the carriers is not consistently constant. On the other hand, a modified formula, called the kink effect factor, is negatively or positively added, simulating solitary heat waves or lattice vibration, which disturb the propagation of carriers and thus influence the source–drain current (IDS). The new statistical standard deviations (δ) are then found to be effectively suppressed as the kink effect is taken into account.

A Threshold‐Voltage and Drain–Source Current Model for Double‐Channel AlxGa1−xN/GaN/AlyGa1−yN/GaN High‐Electron‐Mobility Transistors

A physics‐based threshold voltage and drain–source current model based on double‐channel AlxGa1−xN/GaN/AlyGa1−yN/GaN high‐electron‐mobility transistors (HEMTs) is proposed in this article. Electrons limited in the potential well are derived from ionized donor‐like surface states of the AlxGa1−xN layer. Accumulated 2D electron gases (2DEGs) and positive charges left are equivalent to planar plate capacitors and further form electric fields, weakening the polarization fields in barrier layers. The physical properties of the dual‐channel HEMT are considered holistically rather than two separate and independent single heterojunctions. The effect of the charges and 2DEGs distributed in lower layers on the upper channel is contained in our model as well. Subsequently, a drain–source current model is proposed through coupling the critical electric field with the threshold voltage (VTH). The influence of channel length modulation, short channel effect, self‐heating effect, and kink effect is involved in this model. The accuracy of the proposed models is verified by comparison with technology computer‐aided design simulations and the experimental results. Proposed models can greatly describe the output characteristics, the transmission characteristics, and the relationship between VTH and device parameters of double‐channel AlGaN/GaN HEMTs.

Nanostructured solar cells based on MoO3 film deposition

Electrodeposited molybdenum oxide thin films are used as a buffer layer between the indium tin oxide (ITO) anode and the organic electron acceptor film in organic solar cells. The MoO3 films are deposited at room temperature using a solution of molybdic, acid and citric acid as complexing agents. Such electrodeposited MoO3 ultra thin films (10-20 nm) has been used as buffer layer (BF) in ITO/BF/copper phthalocyanine (CuPc)/fullerene (C60)/ aluminium tri (8-hydroxyquinoline) (Alq3)/ aluminium photovoltaic cells. It is shown that this electrodeposited MoO3 buffer layer enhances the charge transfer from CuPc to ITO through a decrease of the effective barrier, present at the interface CuPc/ITO. This improving effect is directly highlighted by the shape of the J-V curves. The kink effect, due to the barrier present at the interface ITO/organic, disappears when the electrodeposited molybdenum oxide buffer layer, is introduced at this interface, which testifies of the decrease of the barrier.

Performance improvement of junctionless SOI-MOSFETs by a superior depletion technique

This work uses a superior depletion technique to present a junctionless silicon-on-insulator (SOI) metal-oxide field-effect transistor (MOSFET) in a 14 nm regime. The suggested technique embeds a P-type area into the buried silicon oxide (SiO2) layer. The p-silicon area has several effects on the proposed structure (EPB-JLSM): First, it helps us attain a full depletion area in the channel. Second, the self-heating improves due to the higher thermal conductivity of silicon than the silicon nitride. Finally, the embedded area causes the lower hole concentration (high Vds at accumulation mode), resulting in a better kink effect. Also, we discuss the impact of inserting the P-silicon area geometry into the buried layer on the DC performance device, such as height and thickness. The P-silicon area decreases the leakage current (IOFF) by three orders of magnitude (∼1000%), and also slightly enhances the drive current (ION) (∼20%), and reduces subthreshold swing (SS) from 186 to 109 mV dec−1 (∼71%) compared to a typical junctionless SOI MOSFET (C-JLSM). Furthermore, we discuss the effect of the buried region and gate insulator materials on the proposed device’s performance.

Effect of Zn/Y atomic ratio on precipitation behavior and dynamic recrystallization behavior of Mg–Zn–Y alloy under different extrusion temperature

Precipitation behavior and dynamic recrystallization (DRX) behavior of Mg–Zn–Y alloys with different Zn/Y atomic ratios under different extrsuion temperatures were systematically investigated in this work. The results shows that the types of precipitated phases in the casted alloys are changed with the increase of Zn/Y atomic ratio. After extrsuion, the brittle W-phases in Mg98.7Zn1Y0.3 and Mg98Zn1Y1 alloys are broken into finer particles along the extrusion direction, but the resistance of W-phases to grain growth is weak at higher extrusion temperature. However, Mg97.5Zn1Y1.5 alloy exhibits relatively stable grain size at different extrusion temperatures, due to the significant inhibitory effect of LPSO phases on grain growth at high temperatures. The banded LPSO phases with wide phase spacing can promote DRX behavior via particle stimulated nucleation (PSN) resulting in highest DRX fraction. Nevertheless, the lamellar LPSO phases could effectively hinder the grain boundary migration and dislocation motion, which is against the nucleation and growth of DRX grains. It is precisely due to the influence of LSPO phases on the DRX behavior and its own kinking effect that Mg97.5Zn1Y1.5 alloy has better heat resistance. Mg97.5Zn1Y1.5 alloy exhibits excellent tensile strength and ductility, with ultimate tensile strength (UTS) of 413 MPa, yield strength (YS) of 330 MPa and elongation (EL) of 12.1% after extrusion at 573 K. The good ductility is mainly due to the coordinated deformation ability of the LPSO phase and the activated non-basal slip effect. The synergistic effect of lamellar LPSO phase and kinking deformation effectively refines the microstructure of the alloy and improves the strength.

Will Substantial Revaluation of Chinese Currency Be Helpful in Attenuating the United States’ Trade Deficit with China? New Evidence from the Dynamic Threshold Kink Model

ABSTRACT This study explores the possible existence of threshold kink effects in the impact of the real dollar-renminbi exchange rate misalignment on the bilateral trade flows between the United States and China. Empirical results show a significant threshold effect, with differential effects of undervaluation and overvaluation. Specifically, our findings suggest that while an overvaluation of the Chinese currency over 2.83% will attenuate the United States’ trade deficit with China, an undervaluation greater than 4.04% will deepen it. This suggests that a revaluation of the renminbi against the dollar would be helpful in improving the United States trade balance with China.