Carrier Injection Model Research Articles

Substrate noise evaluation for lightly doped 45nm N-MOSFET using physical simulation models

ABSTRACT Analyzing substrate noise for an n-channel MOSFET (NMOS) substrate has been developed using various concepts such as virtual separation concept, p-contact to p-contact model and transistor switching noise model. A design is necessary for the substrate design development to minimize noise in FoMs (Figure Of Merits) and reduce threshold voltage developed noise. In the proposed model, a substrate-induced chip used for finding the noise in drain current has been improved with the increased doping density of an NMOS device. From a substrate noise coupling network with the proposed low signal equivalent circuit, the system measures noise at NMOS substrate using a hot carrier injection model. The proposed concept has been implemented in TCAD-SILVACO software, the design was made in ATHENA, and its corresponding electrical characteristics are simulated by the ATLAS software tool. This model extracts parameters such as overall noise in FoMs, drain current-gate current bias analysis, cross-correlation, and minimized threshold value. After capacitive coupling is achieved over different operation conditions and dimensions, excellent output is from simulated noise data.

Leveraging Public Information to Fit a Compact Hot Carrier Injection Model to a Target Technology

The design of countermeasures against integrated circuit counterfeit recycling requires the ability to simulate aging in CMOS devices. Electronic design automation tools commonly provide this ability; however, their models must be tuned for use with a specific target technology. This requires data which is ideally provided by a fab. It may also be collected from a set of purpose-built test devices, a costly and time-consuming process. Here we describe a novel, low-cost, and rapid approach to tuning such models. Our iterative method leverages public domain data sourced from published studies to fit an aging model. Results are statistically validated against the target technology’s specification. We demonstrate our approach by fitting a compact hot carrier injection degradation model for use with both core and I/O nMOSFETs from a specific 65 nm technology. Our resulting model parameter values are validated with a maximum error of 0.5% with a 99% confidence bound.

Numerical investigation of organic thin-film transistors using a thermionic field emission model

Charge injection barriers at the electrode/semiconductor interface were considered for numerical investigation of electrical characteristics in realistic organic thin-film transistors (OTFTs). A new thermionic field emission (TFE) model, which addresses tunneling of thermally excited electrons, was used as the carrier injection model of OTFTs in this study. Device simulation for an n-channel OTFT with a bottom-gate, bottom-contact configuration was performed with a thin-film organic transistor advanced simulator (TOTAS). Typical electrical characteristics of realistic OTFTs such as severe nonlinearity in output characteristics were reproduced by this simulation using the TFE model. The effects of contact-area-limited doping for n-channel OTFTs were also examined from the simulation results, suggesting that highly doped semiconducting layers prepared over contact electrodes can neutralize the effect of a Schottky energy barrier. Both the simulation technique with the TFE model and the contact-area-limited doping are promising in designing and developing high-performance OTFTs.

Intrinsic difference in Schottky barrier effect for device configuration of organic thin-film transistors

Schottky barrier effect for n-channel organic thin-film transistors (OTFTs) with bottom-gate, top-contact (TC) and bottom-gate, bottom-contact (BC) configuration was examined by using device simulation with a thin-film organic transistor advanced simulator (TOTAS). A thermionic field emission (TFE) model which addresses tunneling of thermally excited electrons was applied as a carrier injection model of OTFTs. Simulation results reveal that the BC configuration is affected by Schottky barrier more severely than the TC configuration under the same condition for device parameters, and that this discrepancy in device characteristics can be completely alleviated by contact-area-limited doping, where highly-doped semiconducting layers are prepared in the neighborhood of contact electrodes. Moreover, the existence of an intrinsic Schottky barrier is indicated even though an ohmic-contact condition is assumed, which becomes more prominent for lower bulk carrier concentration in organic semiconductor. This work suggests the availability of the TFE model for simulating realistic OTFT devices with Schottky contacts. From the simulation results, intrinsic differences in device performance for the TC and BC configurations are discussed.

Study of the electric-pulse-induced resistive switching effects at Pt/PrBa2Cu3Ox interfaces by multi-electrode method

Polycrystalline PrBa2Cu3Ox (PBCO) ceramic is prepared using the conventional solid-state reaction method and then Pt/PBCO/Pt plane structure device is fabricated. A reversible, non-volatile, and bipolar electric-pulse-induced resistance (EPIR) effect are found in the Pt/PBCO/Pt device. In order to determine the key role that controls the EPIR effect, the electrical properties of the Pt/PBCO interfaces and the temperature dependence of the PBCO bulk resistance are investigated by multi-electrode method. The results indicate that the EPIR effect is mainly induced and dominated by the Pt/PBCO interfaces, rather than the PBCO bulk. By analyzing the I–V characteristics of the contact interfaces, the carrier injection model is inferred to explain the EPIR effect.

Injection-limited contact in bottom-contact pentacene organic thin-film transistors

The contact effect in bottom-contact pentacene-based thin-film transistor, with Au source/drain electrode, is investigated. By separating the voltage drop at the source contact from the source-drain voltage, the current–voltage characteristic of the injection contact is obtained. The contact characteristics are in good agreement with a model of carrier injection from a metal electrode into a disordered hopping system.

Validity of Generated Subordinate Carrier Injection Model in Al-profiled HfAlON Dielectrics

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Charge Injection into Bottom-Contact Pentacene Thin-Film Transistors

ABSTRACTWe investigate the contact of bottom-contact pentacene-based thin-film transistors, with Au source/drain electrode. By separating the voltage drop at the contact from the source-drain voltage, the current-voltage characteristic of the injection contact is obtained. The contact characteristics are in a good agreement with a model of carrier injection from a metal electrode into a disordered hopping system.

Electrical properties of fluorine-doped silicon-oxycarbide dielectric barrier for copper interconnect

A fluorine-doped amorphous silicon-oxycarbide (SiCOF) dielectric barrier deposited by chemical vapor deposition system is used to replace nitrogen doped silicon carbide (SiCN) and silicon oxycarbide (SiCO) in the 45nm Cu-interconnect structure due to its low leakage current and dielectric constant. In this article, the low leakage current and dielectric constant of SiCOF mechanism are reported for the first time. The low leakage current of the SiCOF films is due to less trapped sites of electron transportation via Pool-Frenkel model than SiCO. The dangling and weak bonds such as Si–H and –CHx are eliminated by fluorine to form Si–F, and less charge will be trapped in the SiCOF film. A dielectric polarization model is proposed to explain the low dielectric constant of SiCOF. The elimination of molecule dipole is attributed to the incorporated fluorine atoms, which destroy the Si–O–Si tetrahedral network structures. A carrier injection model combined with the polarization is proposed to explain the flatband voltage (Vfb) shift of the C-V curves. The polarization is further verified by using thermal oxide under carbide films to reject the carrier injection from the silicon. At a high electrical field of 2MV∕cm, undoped SiCO has an obvious C-V hysteresis loop, but SiCOF does not. Both at low 1MV∕cm and high 2MV∕cm electric fields SiCOF had a lower C-V hysteresis loop and flatband voltage shift than undoped SiCO. The root causes of this phenomena are the unsaturated bonds in the film and the interface trap sites of SiCO(SiCOF)/silicon elimination. SiCOF is therefore a good candidate as a dielectric barrier for processes with a back end line requirement under 45nm.

A discussion of conduction in organic light-emitting diodes

In general, it is believed that the current in organic light-emitting diodes (OLEDs) occurs as a result of space charge-limited current (SCLC). On the other hand, some researchers have analyzed the current in OLEDs on the basis of the Schottky model. Although the current of OLEDs depends on temperature, i.e. it increases with increasing temperature, it is inferred that it is not controlled only by thermal emission since the charge transfer between molecules is thought to have a positive temperature dependence. The authors have investigated the necessary condition for the SCLC model: the dielectric relaxation time of a material is greater than the carrier drift time between both electrodes in the material. Carrier transport in OLEDs cannot be explained only by the unipolar carrier injection model; it also remains unclear whether hole injection is Ohmic or not. The authors estimated the apparent dielectric relaxation time, τ of OLEDs. Consequently, it was found that the necessary condition of SCLC is not satisfied in the high electric field region.

Electrical instability of low-dielectric constant diffusion barrier film (a-SiC:H) for copper interconnect

An a-SiC:H deposited by CVD system is the most promising dielectric diffusion barrier to replace silicon nitride in the Cu-interconnect structure due to its low dielectric constant, good Cu barrier ability, and low moisture uptake. In this paper, electrical instabilities of a-SiC:H film under electric field were reported for the first time. At electric field higher than 1.8 MV/cm and independent of the polarity, charges will be built up in the SiC film even at room temperature. A dielectric polarization model was proposed to explain this high field instability. The formation of molecular dipole is attributed to the incorporated nitrogen atoms, which distort the symmetric tetrahedral SiC molecule. The dielectric polarization is further verified by the increase of dielectric constant at high temperature and low frequency. At elevated temperature, film instability can be observed at electric field as low as 0.4 MV/cm. A carrier injection model combined with the polarization was proposed to explain the low-field instability. It is assumed that slight polarization occurs at such a low electric field because of high temperature. The dominant mechanism is electron injection from metal gate into SiC film via the Schottky emission process. It is thus recommended that the incorporation of nitrogen must be minimized and the film stability must be carefully evaluated at real circuit level.

Current-Induced Optical Effect in Porous Silicon Fabry-Perot Resonators

The refractive index of porous silicon (PS) was changed by electrical injected carriers in PS-based Fabry-Perot resonator (PS-FPR) diodes. According to measurements of time evolution, there are fast (millisecond order) and slow (several seconds order) components in the refractive index change. This phenomenon can be well explained by a theoretical estimation based on a model of carrier injection and subsequent accumulation. The maximum value of the relative refractive index change is about 0.1% at a diode current density of 40 mA/cm2. These results indicate further technological potential of PS for silicon-based opto-electronic devices.

Current oscillations and stable electric field domains in doped GaAs/AlAs superlattices

The crossover between two regimes has been observed in the vertical electric transport of weakly coupled GaAs/AlAs superlattices (SLs). At fixed d.c. bias, the SLs can be triggered by illumination to switch from a regime of temporal current oscillation to the formation of a stable electric field domain. The conversion can be reversed by raising the sample temperature to about 200 K. An effective carrier injection model is proposed to explain the conversion processes, taking into account the contact resistance originating from DX centres in the contact layers which is sensitive to light illumination and temperature. In addition, quasiperiodic oscillations have been observed at a particular d.c. bias voltage.

Bipolar quantum-transport modeling of carrier injection into a SCH-quantum-well laser

A quantum mechanical model of carrier transport in separate confinement heterostructure (SCH) quantum-well lasers based on the Wigner function is presented for the first time. In the simulation, the three quantum Liouville equations with respect to the Wigner functions defined for electron, heavy-hole, and light-hole are solved simultaneously with the Poisson's equation to consider self-consistency in potential, As a simulation model, InGaAsP-InGaAs SCH quantum-well lasers are considered. The carrier injection into single and double quantum-well lasers is simulated. It is demonstrated that the amount of electrons and holes injected into the single quantum-well active layer is not equal in general if the quantum transport is considered. In the double quantum-well structure, the bottleneck phenomenon of heavy-hole injection into the second well and the quite different shape of heavy-hole density profiles in the two wells are simulated.

Temperature dependent loss and overflow effects in quantum well lasers

We report a detailed study of the temperature dependent internal loss in 1550-nm quantum well lasers. Measurements of lasers with different cavity lengths as well as of lasers with modified facet reflectivities are presented. The internal loss is found to be mainly associated with intervalance band absorption and to include contributions from confined as well as unconfined carriers with the latter dominating at elevated temperatures. Measurements are consistent with calculations based on a detailed carrier injection model. Threshold current density dependence on temperature and on cavity length as well as photon density dependent internal losses are also addressed. >

Transient carrier dynamics and photon-assisted transport in multiple-quantum-well lasers

Time-domain solutions to a detailed carrier injection model for multiple-quantum-well lasers under large signal current step injection is presented. The calculations yield a description of electron and hole carrier density distribution in space, time, and energy and also lead to the identification of a photon-assisted transport mechanism which may have a major impact on the dynamics of lasers with a large number of wells.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Investigation of the low frequency dispersion of InP-oxide using a new Cole-Cole double-arc distribution

A new relaxation time distribution has been developed for double arc Cole-Cole plots in order to study the dispersion relation of InP-oxide. As suggested by a carrier injection model, the low frequency dispersion most likely originates from remaining In at the interface. The presence of In is a direct consequence of the Al electrode formation where the vapor-deposited electrode reacts with the InPO4.

Dielectric and interfacial properties of InP plasma-grown oxides

Methods of dielectric analysis have been employed to investigate the frequency dispersion of InP-oxide dielectric in MOS and MOM devices. The Cole-Cole empirical method has indicated a wide range of relaxation time for the interfacial polarization. This has been interpreted in terms of a model of carrier injection from the gate metal into the oxide gap states. The model is proposed in conjunction with the anomalous hysteresis in the MOM C-V characteristics and could be applied to other MIS systems.

Time-resolved measurement of the escape of charge carriers from a Coulombic potential well by diffusional motion

The irreversible escape of charge carriers from the bottom of a coulombic potential well over the barrier by diffusional motion has been measured, for the first time, directly as a rise time of 1 ns time-resolved current transients in anthracene single crystals with electrolytic contacts. The observed steep decrease in the characteristic escape time down to 1 ns, with rising electric field up to 1×105 V cm−1, is in excellent agreement with the predictions of a stationary one-dimensional charge carrier injection model with generalized boundary conditions. The electric field dependence of the rate constant for escape cannot be approximated simply by an exponential dependence on the barrier height, as in the familiar Schottky correction for the case of electron emission or in the Poole–Frenkel formula for change carrier escape from a charged trap. As a side result, the hole mobility in the c′ direction of anthracene single crystals has been found constant μ = 0.85±0.05 cm2 V s−1 up to an electric field strength of 5±105 V cm−1 at room temperature.

Injection charging of polymeric capacitors

The charging of non-polymer capacitors due to a step voltage is studied as a function of time. Apart from the classical charging, which is completed in nanoseconds, it is found that the current flowing into the capacitor can be described as a sum of two exponential functions of time, the time constants differing by a factor of ten or more. In the case of polyethylene, at least, it is clear that the shorter time constant is connected with carrier injection into the polymer from the metal surface. The longer time constant is presumably due to carrier migration within the volume of the dielectric. These findings may be correlated with our previous results on the field dependence of electrostatic charging and support the model of carrier injection to a finite depth.