Deep Depletion Research Articles

Evaluation of polarization characteristics in metal/ferroelectric/semiconductor capacitors and ferroelectric field-effect transistors

In this study, we propose a measurement technique for evaluating ferroelectric polarization characteristics in ferroelectric field-effect transistors (FeFETs). Different from standard metal/ferroelectric/metal capacitors, the depletion and inversion phenomena in semiconductor substrates have to be carefully taken into account when evaluating the ferroelectric properties using fast voltage sweep as input. The non-equilibrium deep depletion is found to be the limiting factor for the accurate evaluation of ferroelectric properties in metal/ferroelectric/semiconductor capacitors. By connecting the source, the drain, and the substrate of the FeFET together during the polarization measurement, the deep depletion can be suppressed and the ferroelectricity of the ferroelectric gate can be accurately evaluated. The present technique is a powerful method for capturing the polarization states in FeFETs, enabling new approaches for device characterization and fundamental study, and overcomes the limitation found in the conventional polarization measurement on two-terminal metal/ferroelectric/semiconductor capacitors.

Prolonged Transient Behavior of Ultrathin Oxide MIS-Tunneling Diode Induced by Deep Depletion of Surrounded Coupling Electrode

In this article, the prolonged transient current and the coupled voltage retention behavior of ultrathin oxide MISTD induced by deep depletion of surrounded coupling electrode is investigated. The transient current is induced to balance the surrounded coupling electrode returning to its thermal equilibrium state, and the coupling voltage sensed is the result of the perturbation by the nearby deep depletion. The prolonged transient behavior of the sensed current is explained by the modulation of the hole leakage from the ring metal-insulator-semiconductor (MIS). Also, the behavior of the coupled voltage retention is the result of the generated electrons being swept toward the ring MIS by lateral field. The oxide thickness, coupling gap width, and trapping charges were shown to have influences on both behaviors. Moreover, the sensed coupled voltage of the center MISTD are utilized as memory characteristic and the operation of the proposed MIS memory cell is demonstrated. Oxide thickness smaller than 26 A was proposed for the prolonged transient phenomenon. The power consumption of this device is very low due to limited saturation current.

Water use characteristics of the common tree species in different plantation types in the Loess Plateau of China

Knowledge concerning the water use characteristics of revegetated species has profound implications for understanding soil–plant interaction mechanisms and guiding ecological restoration strategies in water-limited ecosystems. Although afforestation is an important way to improve ecosystem functions and services in degraded ecosystems, there is limited understanding about the water use characteristics of dominant species within and between different types of plantations. We investigated plant water use characteristics in three representative types of plantations on the Chinese Loess Plateau: mixed plantation consisting of three deciduous tree species Robinia pseudoacacia, Armeniaca sibirica and Ailanthus altissima (Mspa), pure R. pseudoacacia plantation (Pp) and pure A. sibirica plantation (Ps). We measured the leaf δ13C of the dominant species within each plantation type and the δ2H and δ18O of xylem and soil water within 400 cm of the soil surface. The results showed that three main species in the mixed plantation exhibited significant difference (p < 0.05) in proportional contributions of water sources, suggesting that the plants had water source segregation. A. sibirica in the mixed plantation utilized more proportional shallow soil water than that in the pure plantation and correspondingly lessened deep soil water depletion. However, no significant difference was found in the water uptake proportions of R. pseudoacacia between the different plantation types. The leaf δ13C values of the plant species in the mixed plantation were significantly higher than those in the pure plantations. The leaf δ13C values of R. pseudoacacia under different plantation were positively associated with SWCs, but this relationship was not observed in A. sibirica. These results indicate that plantation type affected plant water use characteristics with species-specific responses to plantation type and different water source competition effects between interspecific versus intraspecific competition.

Analysis of the Influence of Silicon-on-Insulator Lateral Double-Diffused MOS Device Substrate Deep Depletion on the Transient Breakdown Voltage

With two-dimensional device simulation software, the influence of the deep depletion (DD) of the silicon-on-insulator (SOI) lateral double-diffused metal-oxide-semiconductor (LDMOS) device substrate on the transient breakdown voltage (TrBV) was analyzed. Based on the changes in the characteristics of the charge distribution and the depletion layer in the device substrate with time and the related parameters in the off state, the mechanism of their action on the transverse and vertical breakdown voltages (BVs) was studied. TrBV demonstrates completely different characteristics from the static breakdown voltage (StBV) due to the DD effect of SOI LDMOSs. Low drift region concentration (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ) and substrate doping concentration (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub</sub> ) are conducive to obtaining a high maximum TrBV. With increasing drain voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ), the turn-off nonbreakdown time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nonbv</sub> ) of the device with higher P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub</sub> decreases faster. However, the T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nonbv</sub> with higher P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub</sub> is higher at low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> . Therefore, the maximum T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nonbv</sub> can be obtained by optimizing N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> and P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub</sub> under a given V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> . In addition, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nonbv</sub> is greatly reduced with increasing temperature.

Negative Capacitance Double-Gate Junctionless FETs: A Charge-Based Modeling Investigation of Swing, Overdrive and Short Channel Effect

In this article, an analytical predictive model of the negative capacitance (NC) effect in symmetric long channel double-gate junctionless transistor is proposed based on a charge-based model. In particular, we have investigated the effect of the thickness of the ferroelectric on the I-V characteristics. Importantly, our model predicts that the negative capacitance minimizes short channel effects and enhances current overdrive, enabling both low power operation and more efficient transistor size scaling, while the effect on reducing subthreshold slope shows systematic improvement, with subthermionic subthreshold slope values at high current levels. Our predictive results in a long channel junctionless with NC show an improvement in ON current by a factor of 6 in comparison to junctionless FET. The set of equations can be used as a basis to explore how such a technology booster and its scaling will impact the main figures of merit of the device in terms of power performances and gives a clear understanding of the device physics. The validity of the analytical model is confirmed by extensive comparisons with numerical TCAD simulations in all regions of operation, from deep depletion to accumulation and from linear to saturation.

Modeling Interface Charge Traps in Junctionless FETs, Including Temperature Effects

In this paper, an analytical predictive model of interface charge traps in symmetric long channel double-gate junctionless transistors is proposed based on a charge-based model. Interface charge traps arising from the exposure to chemicals, high-energy ionizing radiation or aging mechanism could degrade the charge-voltage characteristics. The model is predictive in a range of temperature from 77K to 400K. The validity of the approach is confirmed by extensive comparisons with numerical TCAD simulations in all regions of operation from deep depletion to accumulation and linear to saturation.

Ac conductivity and impedance spectroscopy study and dielectric response of MgPc/GaAs organic heterojunction for solar energy application

The study concerns the C/ω-V performances and examination of dielectric response of MgPc/GaAs organic heterojunction (OHJ) structure of solar energy applications. Throughout this work, many characterizations have been achieved and various parameters have been extracted. C/ω-V and G/ω-V plots are subject to give much knowledge about the mechanism and behavior inside the OHJ. It is revealed that capacitance of OHJ increases with voltage defining deep depletion (dd), depletion (dep) and accumulation (ac) regions. Besides, Ac conductivity at room temperature increases with frequency in particular within the forward biasing voltage, reaching a high point of 28 × 10−7 S/cm at 5 V. Real and imaginary terms of complex dielectric constant or well known by permittivity, ε versus lnω are studied inside the 1.5V–2.5 V range. The real and imaginary parts of the impedance are found to be frequency dependence within the 1.5 V and 2.5 V bias range. Ac current conductivity σAc against frequency (lnω) of MgPc/GaAs OHJ inside 1.5V–2.5 V bias voltage range is well detailled; the average of conductivity about 8 × 10−7 S/cm is then recorded. The impedance spectroscopy study is evidenced by the complex impedance M where real and imaginary part are M′ and M’’. Profile of M′ and M″ as function of voltage exhibits peaks for 3 kHz–300kHz frequency range. It is indicated that M″ and M’ are roughly comprised between 0.08 and 1.12 and 0 and 2 respectively. Conduction mechanism is then determined by lnσ-lnω plots. The Cole-Cole diagram displays different curves of impedance as distinct semicircle for measured frequencies.

Vanadium cycling in the Western Arctic Ocean is influenced by shelf-basin connectivity

Water in the western Arctic Ocean tends to show lower dissolved vanadium concentrations than profiles observed elsewhere in the open ocean. Dissolved V in Pacific-derived basin waters was depleted by approximately 15–30% from the effective Pacific Ocean endmember. The depletion originates on western Arctic shelves and is not a result of mixing with a water mass with low V. While biological uptake may account for some of the V removal from the water column, adsorption onto particulate Fe is likely the dominant factor in removing V from shelf waters to the sediments. Once in the sediments, reduction should result in sequestering the V while Fe (and Mn) can be remobilized. A similar Fe-shuttling mechanism for V was previously described for the Peru margin (Scholz et al. 2011). Off the shelves, particulate Mn concentrations often exceed particulate Fe concentrations and thus may exert greater control on the V distribution in basin waters. Nonetheless, particulate V concentrations are much lower in basin waters and dissolved V thus behaves largely conservatively away from the shelf environment. Dissolved V concentrations in Atlantic-derived and Arctic deep waters were as much as 5 nmol/kg lower than those observed in deep waters of other ocean basins. The uniformity in deep water dissolved V between the sampled basins suggests that slow removal of V from the deep basins is probably not a factor in the deep water depletion. Vanadium-depleted incoming Atlantic waters (i.e., the source of Arctic deep waters) and/or removal of vanadium from incoming waters that pass over the shelves probably accounts for the deep water dissolved V depletion. Overall, our results demonstrate the utility of the V distribution as an additional tool to help understand the Arctic marine system. Furthermore, our work is pertinent to questions related to the net effect of marginal basin shelves on oceanic vanadium cycling, its isotopic balance, and how climate-induced changes in shelf biogeochemical cycling will impact vanadium cycling.

Ultrathin Junctionless Nanowire FET Model, Including 2-D Quantum Confinements

In this paper, we develop an explicit model to predict the dc electrical behavior in ultrathin surrounding gate junctionless (JL) nanowire field-effect transistors (FETs). The proposed model considers 2-D electrical and geometrical confinements of carrier charge density within few discrete subbands. Combining a parabolic approximation of the Poisson equation, the first-order perturbation theory for the Schrodinger subband energy eigen-values and the Fermi–Dirac statistics for the confined carrier density lead to an explicit solution of the dc characteristic in ultrathin JL devices. Validity of the model has been verified with technology computer-aided design simulations. The results confirm its validity for all regions of operation, i.e., from deep depletion to accumulation and from linear to saturation. This represents an essential step toward analysis of circuits based on JL nanowire devices.

A Novel One-Transistor Active Pixel Sensor With In-Situ Photoelectron Sensing in 22 nm FD-SOI Technology

For the first time, a novel active pixel sensor (APS) with 22 nm fully depleted silicon-on-insulator (FD-SOI) technology is experimentally demonstrated. The APS in-situ integrates photo sensing, charge integration, buffer amplification, and random access in one transistor without charge transfer and assistance of additional transistors. The deep depletion effect in the substrate of the SOI MOSFET is used to collect photoelectrons which are then sensed by the top Si channel. A sensor array is proposed and high sensitivity is experimentally verified in a simplified circuit.

Structural and compositional modification of graphene oxide by means of medium and heavy ion implantation

Graphene and its allotropes belong to the new generation of materials. Due to their extraordinary electrical, mechanical and other properties, their application possibilities are vast. In this work, a study on interactions of graphene oxide (GO) layers using Au and Ga ions with energy of 40 keV was realized. Very shallow layers of GO are modified as low energy ions are depositing energy mostly in the upper layer due to the low projected ion ranges at most of 50 nm. The ion irradiation fluences of 5.0 × 1014 cm−2, 5.0 × 1015 cm−2 and 5.0 × 1016 cm−2 were used. Upon irradiation, the modified GO foils were characterised using nuclear analytical methods – Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection Analysis (ERDA) and various conventional analytical methods such as Raman spectroscopy, Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), and 2-point conductivity measurements. Oxygen species removal was evidenced as the increasing function of the ion implantation fluence and oxygen depth profiles exhibited complex behaviour connected to implanted ion specie. The deep oxygen depletion in the broad surface layer accompanied by Ga diffusion into the depth was observed in Ga irradiated GO compared to Au irradiated samples which exhibited a narrow oxygen depleted layer at GO surface. XPS evidenced strong increase of CC bonds compared to CO bonds on the irradiated GO surface with increasing ion fluence, which was comparable for both ion species. Raman spectroscopy shows the modification of main phonon modes identified in GO. The D peak slight decrease and broadening was observed for GO irradiated with ion fluence above 5 × 1015 cm−2 and mainly for Au ion irradiation. FTIR analysis proved the oxygen containing functional group release with the increased ion fluence, mainly CO group release after Au ion irradiation was observed. Simultaneously HO stretching absorption peak is in FTIR spectrum reduced more significantly for Ga irradiated GO which is in accordance with RBS elemental analysis exhibiting the more pronounced hydrogen depletion. Electrical conductivity measurement shows the linear I-V characteristics for the GO irradiated using both ion species and all ion fluences; the surface layer exhibited conductive behaviour comparing to pristine GO non-linear I-V characteristics.

Determination of the Parameters of Metal–Insulator–Semiconductor Structures with Ultrathin Insulating Layer from High-Frequency Capacitance–Voltage Measurements

A simple numerical method for processing the data of the high-frequency capacitance–voltage characteristics of metal–insulator–semiconductor structures is proposed. The approach is based on analyzing the experimental characteristics near the flat-band states, where the charge exchange of surface localized electron states is of little importance compared with changes in the near-boundary charged layer in the semiconductor. The developed technique makes it possible, first, to find the necessary parameters of the semiconductor and insulating layer and, second, to obtain the experimental field dependences of the energy-band bending in the semiconductor and the total concentration of the built-in charge, the charge of boundary states and minority charge carriers at the semiconductor–insulator interface in the range from the flat bands to deep depletion. The technique is well applicable to structures with an ultra-thin insulating layer. On n-Si-based metal–oxide–semiconductor samples with an oxide thickness of 39 A, experimental approbation of the proposed approach is carried out. The accuracy of the obtained results is 2–3%.

Определение параметров структур металл-диэлектрик- полупроводник со сверхтонким изолирующим слоем из высокочастотных вольт-фарадных характеристик

AbstractA simple numerical method for processing the data of the high-frequency capacitance–voltage characteristics of metal–insulator–semiconductor structures is proposed. The approach is based on analyzing the experimental characteristics near the flat-band states, where the charge exchange of surface localized electron states is of little importance compared with changes in the near-boundary charged layer in the semiconductor. The developed technique makes it possible, first, to find the necessary parameters of the semiconductor and insulating layer and, second, to obtain the experimental field dependences of the energy-band bending in the semiconductor and the total concentration of the built-in charge, the charge of boundary states and minority charge carriers at the semiconductor–insulator interface in the range from the flat bands to deep depletion. The technique is well applicable to structures with an ultra-thin insulating layer. On n -Si-based metal–oxide–semiconductor samples with an oxide thickness of 39 Å, experimental approbation of the proposed approach is carried out. The accuracy of the obtained results is 2–3%.

Regional differentiation of foliar N/Ca in Fagus americana and F. sylvatica on acid soils

Prolonged periods of air pollution depleted soil Ca and increased N supply in forests of Eastern North America and Central Europe. We compared a cool rural to a warm urban forest site to explore the geographic range of foliar N, Ca, and N/Ca on naturally regenerated saplings of American beech and European beech in Nova Scotia (Canada) and Saarland (Germany), respectively. Foliar N/Ca of beech saplings remained variable due to geo-climatic gradients and bio-climatic site factors, tight internal cycling of Ca, and varying pollution history. Our data suggest that deep and extreme soil Ca depletion renders climatic factors the drivers of foliar N/Ca in beech forests. Global warming will therefore amplify the potential risks of changing nutrient supply ratios in regions with a prolonged history of severe acid rain. Existing forest site classifications usually capture regional differentiation of climatic factors but often fail to assess impacts of acid rain history on foliar Ca that will be required for regional differentiation of foliar nutrient ratios on acid soils. However, homogenization of foliar Ca can be expected in regions with a history of severe acid rain.

Iodine doping enabled wide range threshold voltage modulation in pentacene transistors

We demonstrate an ultra-high range of threshold voltage modulation in pentacene transistors by iodine doping. Through diffusion control and thermal treatments, the transistor's threshold voltage can be tuned in a wide range of more than 100 V from enhance mode to deep depletion mode. The correlation between physical and electrical characteristics was investigated to elucidate the modulation mechanism. The results suggest an optimistic potential for pentacene transistors in high voltage device applications. The transistors in this research exhibit a high field effect mobility of ~0.18 cm2/Vs and on/off ratio ~105.

Charge-Based Model for Ultrathin Junctionless DG FETs, Including Quantum Confinement

This paper presents a generalization of the charge-based model for ultrathin junctionless double-gate (JLDG) field-effect transistors (FETs) by including quantum electron density. The analytical derivation relies on a first-order correction to the infinite quantum well. When restricting the analysis to the first and second quantized states, the free carrier charge distribution and the current in an ultrathin body JLDG FETs are in agreement with numerical TCAD simulations in all the regions of operation, i.e., from deep depletion to accumulation and from linear to saturation.

Gate Oxide Electrical Stability of p-type Diamond MOS Capacitors

This paper shows the effect of performing consecutive measurement prior to negative bias stress instability (NBSI) on diamond metal–oxide–semiconductor capacitor (MOSCAP). For the first time, time-dependent stress tests have been carried out in order to investigate the stability of the flatband voltage ( ${V}_{\text {FB}}$ ) of MOSCAPs through capacitance–voltage ( CV ) measurements. Two tests have been performed. In the first test, consecutive CV measurements with the device biased from deep depletion to the accumulation regime were performed to monitor the recovery of the ${V}_{\text {FB}}$ . In the second test, NBSI technique has been applied. ${V}_{\text {FB}}$ stability has been measured by means of a time-dependent bias stress in which the device was polarized at a fixed negative voltage for a specific time interval prior to performing the next CV measurement. As ${V}_{\text {FB}}$ is directly connected to the effective oxide charge ( ${N}_{\text {eff}}$ ), the two different tests allowed the extraction of total amount of ${N}_{\text {eff}}$ that interfered during the measurements. The result observed shows that the postoxidation annealing process induces a strong enhancement of the MOSCAP stability together with a decrease of ${N}_{\text {eff}}$

Modeling the Depletion and Recovery of the Outer Radiation Belt During a Geomagnetic Storm: Combined MHD and Test Particle Simulations

AbstractDuring geomagnetic storms the intensities of the outer radiation belt electron population can exhibit dramatic variability. Deep depletions in intensity during the main phase are followed by increases during the recovery phase, often to levels that significantly exceed their prestorm values. To study these processes, we simulate the evolution of the outer radiation belt during the 17 March 2013 geomagnetic storm using our newly developed radiation belt model (Conservative Hamiltonian Integrator for Magnetospheric Particles) based on test particle and coupled 3‐D ring current and global magnetohydrodynamic (MHD) simulations, and driven solely with solar wind and F10.7 flux data. Our approach differs from previous work in that we use MHD information to identify regions of strong, bursty, and azimuthally localized earthward convection in the magnetotail where test particles are then seeded. We validate our model using in situ Van Allen Probe electron intensities over a multiday period and show that our model is able to reproduce meaningful qualitative and quantitative agreement. Analysis of our model enables us to study the processes that govern the transition from the prestorm to poststorm outer belt. Our analysis demonstrates that during the early main phase of the storm the preexisting outer belt is largely wiped out via magnetopause losses, and subsequently, a new outer belt is created during a handful of discrete, mesoscale injections. Finally, we demonstrate the potential importance of magnetic gradient trapping in the transport and energization of outer belt electrons using a controlled numerical experiment.

Charge-based Model for Junction FETs

We present a unified charge-based model for double-gate and cylindrical architectures of junction field-effect transistors (JFETs). The central concept is to consider the JFET as a junctionless FET (JLFET) with an infinitely thin insulating layer, leading to analytical expressions between charge densities, current, and voltages without any fitting parameters. Assessment of the model with numerical technology computer-aided design simulations confirms that holding the JFET as a special case of the JLFET is justified in all the regions of operation, i.e., from deep depletion to flat-band and from linear to saturation.

Photo Sensitivity Enhanced by the Modulation of Oxide Thickness in MIS(p) Structure

Photodetector for MIS(p) structure with surrounding concentric gate resulted in significant interest. We propose the modulation of oxide thickness to improve the sensitivity of the photodetector. By measuring various oxide thickness from 2.2 to 3.4 nm, we find that the dark current under deep depletion region of MIS structure strongly depends on oxide thickness. As the oxide thickness increases, the dark current in center MIS decreases and thus effectively increases the sensitivity. We suggest that the reduced dark current resulted from less modulation of Schottky barrier height while surrounding gate current of the thick device is lower. By properly biasing the gate electrode, the ratio of light to dark current of MIS structure is 9 for 2.5nm but is 148 for 3nm. The sensitivity of the thick oxide device is enhanced to 16 times with respect to the thin one.