Showing papers in "Solid-state Electronics in 1991"
TL;DR: In this article, the authors presented simple but accurate closed form equations for band gap narrowing (BGN) for n and p type, Si, Ge, GaAs and GexSi1−x alloys and strained layers.
Abstract: This paper presents simple but accurate closed form equations for Band Gap Narrowing (BGN) for n and p type, Si, Ge, GaAs and GexSi1−x alloys and strained layers The equations are derived by identifying the four components of BGN: exchange energy shift of the majority band edge, correlation energy shift of the minority band edge and impurity interaction shifts of the two band edges In the simple parabolic band approximation, the BGN is determined by the effective masses of the carriers and the relative permittivity of the semiconductor For real semiconductors, known corrections due to anisotropy of the bands, due to multi-valleys in a band and due to interactions between sub-bands are used The values of BGN for n Si, n Ge and n and p GaAs calculated using this simple formulation agree closely with the theoretical values calculated by other authors using advanced but complex many body methods and the Random Phase Approximation for screening effects For p Si and p Ge ours appear to be the first calculations taking all interactions into account Experimental values of BGN for all semiconductors except for p Ge for which no data could be found, are also in very good agreement with our theory The Fermi level for n and p Si and p GaAs is determined using the published luminescence data In heavily doped p type semiconductors, the values are found to be considerably smaller than those calculated using the known values of the effective density of states The values of apparent BGN for n and p Si and p GaAs calculated using experimentally determined Fermi levels are in remarkably good agreement with the experimental values derived from device measurements All results are presented in a form which lends itself to numerical computer simulation studies
376 citations
TL;DR: In this article, the contribution of thermionic-emission current and various other current-transport mechanisms were assumed when evaluating the Schottky barrier height Φ 0.881 ± 0.002 eV was reached independent of temperature.
Abstract: I–V Measurements on PtSi-Si Schottky structures in a wide temperature range from 90 to 350 K were carried out. The contributions of thermionic-emission current and various other current-transport mechanisms were assumed when evaluating the Schottky barrier height Φ0. Thus the generation-recombination, tunneling and leak currents caused by inhomogeneities and defects at the metal-semiconductor interface were taken into account.
Taking the above-mentioned mechanisms and their temperature dependence into consideration in the Schottky diode model, an outstanding agreement between theory and experiment was achieved in a wide temperature range.
Excluding the secondary current-transport mechanisms from the total current, a more exact value of the thermionic-emission saturation current Ite and thus a more accurate value ofΦb was reached.
The barrier height Φb and the modified Richardson constant A∗∗ were calculated from the plot of thermionic-emission saturation current Ite as a function of temperature too. The proposed method of finding Φb is independent of the exact values of the metal-semiconductor contact area A and of the modified Richardson constant A∗∗. This fact can be used for determination of Φb in new Schottky structures based on multicomponent semiconductor materials.
Using the experimentally evaluated value A∗∗ = 1.796 × 106Am−2K−2 for the barrier height determination from I–V characteristics the value of Φb = 0.881 ± 0.002 eV was reached independent of temperature.
The more exact value of barrier height Φb is a relevant input parameter for Schottky diode computer-aided modeling and simulation, which provided a closer correlation between the experimental and theoretical characteristics.
164 citations
TL;DR: In this article, the authors present the development of rugged high-current (100 A range) low-voltage trench DMOS transistors, featuring 4 mΩ on-resistance, with controlled bulk avalanche breakdown at 70 V and gate dielectric breakdown at 60 V.
Abstract: Design and processing concepts are presented that have led to the development of rugged high-current (100 A range) low-voltage trench DMOS transistors, featuring 4 mΩ on-resistance, with controlled bulk avalanche breakdown at 70 V and gate dielectric breakdown at 60 V. The results of a simulation-based investigation are also presented, revealing that the trench DMOS technology has at least a factor-of-two die area advantage over its planar DMOS counterpart in the range from low (50 V) to medium (200 V) voltages.
116 citations
TL;DR: In this article, a computationally efficient technique for obtaining the electron velocity distribution function in silicon is presented, where analytical methods using Legendre polynomials are combined with numerical techniques using matrices to solve the Boltzmann transport equation.
Abstract: A computationally very efficient technique for obtaining the electron velocity distribution function in silicon is presented. Analytical methods using Legendre polynomials are combined with numerical techniques using matrices to solve the Boltzmann transport equation. Results agree with Monte Carlo calculations, but are obtained in approx. 1 100 the CPU time. The method accounts for the effects of acoustic and intervalley phonon scattering, as well as silicon's nonparabolic, ellipsoidal band structure. Accurate expressions for electron average energy, drift velocity and mobility in terms of the distribution function are also provided. The method is appropriate for use in CAD tools for semiconductor devices.
98 citations
TL;DR: In this article, a functional form of Green's theorem for inhomogeneous media with electrodes maintained at constant potentials has been introduced, which is an extension of Ramo's original proof and is different from the energy balance method which is the existing method of proof of the theorem at constant electrode potentials.
Abstract: An introduction of a new functional form of Green's theorem for inhomogeneous media has enabled us to show that the Ramo-Shockley theorem derived for inhomogeneous media with electrodes maintained at constant potentials is still valid even when the electrode potentials are time-varying. Our proof, which is based on this modified Green's theorem, is an extension of Ramo's original proof and is different from the energy balance method which is the existing method of proof of the theorem for inhomogeneous media at constant electrode potentials. Our proof provides a basis for calculations of the instantaneous currents in semiconductor devices using particle simulations such as the Monte-Carlo method since it differentiates clearly the current induced in the electrodes due to the moving charges from the current caused by the time-varying potentials of the electrodes through capacitive couplings among the electrodes.
96 citations
TL;DR: In this paper, a physically-based semi-empirical equation for electron effective mobility in MOS inversion layers has been developed by accounting explicitly for surface roughness scattering and screened Coulomb scattering in addition to phonon scattering.
Abstract: A new physically-based semi-empirical equation for electron effective mobility in MOS inversion layers has been developed by accounting explicitly for surface roughness scattering and screened Coulomb scattering in addition to phonon scattering. The new semi-empirical model shows excellent agreement with experimentally measured effective mobility data from five different published sources for a wide range of effective transverse field, channel doping, fixed interface charge, longitudinal field and temperature. By accounting for screened Coulomb scattering due to doping impurities in the channel, our model describes very well the roll-off of effective mobility in the low field (threshold) region for a wide range of channel doping level ( N A = 3.9 × 10 15 −7.7 × 10 17 cm −3 ). We have also developed a local-field-dependent mobility model for electrons in the inversion layer for use in device simulators by applying the previously published method to this new semi-empirical equation for the effective mobility. The new local-field-dependent mobility model has been implemented in the PISCES 2-D device simulation program, and comparisons of calculated vs measured data show excellent agreement for I D − V G and I D − V D curves for different devices with L eff ranging from 0.5 to 1.2 μ.
88 citations
TL;DR: A method to fabricate Au-n -type InP Schottky contacts with an interfacial layer has been developed in this paper, which is formed by deposition of a P x O y layer and reaction of this layer with the InP substrate.
Abstract: A method to fabricate Au- n -type InP Schottky contacts with an interfacial layer has been developed. The interfacial layer is formed by deposition of a P x O y layer and reaction of this layer with the InP substrate. The current-voltage and capacitance-voltage characteristics are measured at various temperatures. Excellent rectification is found in the fabricated contacts. The observed reverse currents are very low. The ideality factors are around 1.15. Apparent barrier heights qφ B are evaluated from the extrapolated forward saturation current I s . They are found to be sufficiently high. The typical value of qφ B at room temperature is obtained as 0.88 eV. The Richardson plot ln( I s / T 2 ) vs 1/ T is well fitted in a straight line, where T is the temperature. From the Richardson plot, the true barrier height is estimated to be 0.41 eV. The effects of the interfacial layer are also discussed.
78 citations
IBM1
TL;DR: In this paper, the Schottky-barrier heights of W and its silicide WSi2 on both n-type and p-type Si(100) have been measured in the temperature range 77-295 K with the use of currentvoltage and capacitance-voltage techniques.
Abstract: The Schottky-barrier heights of W and its silicide WSi2 on both n-type and p-type Si(100) have been measured in the temperature range 77–295 K with the use of current-voltage and capacitance-voltage techniques. Auger-electron and X-ray photoemission spectroscopies were used to characterize the Si(100) surfaces prior to metal deposition, and to monitor the reaction between W and Si. Silicide formation has very little or no effect on both the barrier height and its temperature dependence. The n-type barrier height for both the metal and the reacted silicide phase decreases with increasing temperature with a coefficient almost equal to the temperature coefficient of the indirect band gap in Si. The p-type barrier height does not exhibit a temperature dependence. These results suggest that the Fermi level at the interface is pinned relative to the valence-band edge. These results deviate from the predictions of models of Schottky-barrier formation based on the suggestion of Fermi-level pinning in the center of the semiconductor indirect band gap. Along with results previously reported for metal(silicide)-Si systems with a wide range in metal electronegativity, the present results show that both the silicon barrier height and its temperature dependence are affected by the metal.
75 citations
TL;DR: In this article, a spin-dependent enhancement of free-carrier capture processes can occur directly at a paramagnetic deep defect without the need for other defects nearby, which is consistent with new experimental results which indicate the absence of any adjacent trapping centers.
Abstract: This paper presents a new model for spin-dependent recombination and generation processes based on the electrical detection of magnetic resonance in semiconductor p - n junction diodes. Based on a modified Shockley-Read recombination statistics, this model differs from those models previously proposed in that the spin-dependent enhancement of free-carrier capture processes can occur directly at a paramagnetic deep defect without the need for other defects nearby. This model incorporates singlet-triplet mechanisms of existing models, but is shown to be consistent with new experimental results which indicate the absence of any adjacent trapping centers.
62 citations
TL;DR: In this article, the authors discuss the problems surrounding quantum 1 ƒf noise and 1 ǫf noise in general, and conclude that many of the problems are solved and do not contribute an enigma any more.
Abstract: In this survey article we discuss the problems surrounding quantum 1 ƒf noise and 1 ƒf noise in general. First we present a short history of quantum 1 ƒf noise concepts, since its inception by Handel in 1975 as effect caused by the infrared correction of cross sections and scattering rates. Next, we summarize the result of our recent quantum electrodynamical (QED) theory based on electron-photon interaction (without the lengthy and cumbersome derivations presented elsewhere). These results fully confirm Handel's basic results for quantum 1 ƒf noise of electromagnetic origin associated with scattering in solids, giving rise to mobility fluctuations; this noise is essential and unavoidable, like Nyquist noise and g-r noise. Other aspects of the quantum 1 ƒf noise formalism are not upheld; in particular we discuss at length the problem of other infra-particle 1 ƒf noise (“general quantum 1 ƒf noise principle” and “phonon bremsstrahlung”), quantum 1 ƒf noise associated with capture or emission processes (among other effects the alpha-particle flicker floor) and the non-existence (classically and quantum electrodynamically) of collision-free linear acceleration noise (“transit noise” in vacuum tubes and L2 dependence noise in solids). Finally, we indicate that many 1 ƒf noise problems are solved and do not contribute an “enigma” any more (many aspects of noise in metals, number fluctuations in semiconductors, low αH mobility-fluctuation noise). On the contrary, more research is necessary to explain high αH mobility-fluctuation noise and some modulation-noise models are suggested.
56 citations
TL;DR: In this paper, the leakage current, hydrogenation mechanism and mobility of poly-Si thin-film transistors were investigated and it was found that hydrogenation proceeds by a lateral penetration through the gate oxide around the edges of the polySi gate finger, leading to channel length dependence of sub-threshold slope in partially hydrogenated devices.
Abstract: There is developing interest in using thin film transistors as active elements in a range of large area electronics applications The characteristics of poly-Si thin film transistors (TFTs), processed at glass compatible temperatures, have been investigated The particular features examined were the leakage current, hydrogenation mechanism and mobility The hydrogenation was found to proceed by a lateral penetration through the gate oxide around the edges of the poly-Si gate finger This led to a channel length dependence of sub-threshold slope in partially hydrogenated devices In contrast, the leakage current, which was shown to be a generation current at the drain junction, did not require hydrogen penetration into the centre of the channel and hence passivation of the generation centres was channel length independent The hydrogen diffusion coefficient in fine grain poly-Si was estimated at 350°C to be ∼1–10 × 10 −14 cm 2 / s depending upon the detailed material properties Thermal crystallisation of LPCVD and PECVD amorphous silicon was found to be comparable with both leading to large dendritic grains and enhanced carrier mobility
TL;DR: In this paper, the lifetime and surface recombination velocity in InP were discussed and it was shown that carrier trapping may be important in the interpretation of transient lifetime measurements, indicating pinning of the surface Fermi level.
Abstract: Lifetime and surface recombination velocity in InP are discussed in this paper. It is shown that carrier trapping may be important in the interpretation of transient lifetime measurements. The surface recombination velocity is found to be doping dependent, indicating pinning of the surface Fermi level. The effects of the surface Fermi level on the surface recombination velocity and the surface generation velocity are used to study the Fermi level pinning at the surface of InP. The capture cross-sections of surface states are estimated to be on the order of 1 × 10−13 cm2.
TL;DR: In this article, a new theory is presented for calculating the avalanche multiplication factor M(x) in semiconductors, which takes into account that a particle has to gain a critical energy Uc (threshold energy) from the electric field E(x), in order to be able to ionize lattice and impurity atoms.
Abstract: A new theory is presented for calculating the avalanche multiplication factor M(x) in semiconductors. The integral equation, which determines M(x), takes into account that a particle has to gain a critical energy Uc (threshold energy) from the electric field E(x) in order to be able to ionize lattice and impurity atoms. Therefore, our theory is also applicable to narrow junctions. The input to our theory are the mean free paths and the threshold energies of electrons (Ln, Ucn) and holes (Lp, Ucp), respectively. Approximations to the integral equation for M(x) lead to ionization rates αn(E), αp(E) for electrons and holes, respectively. The dependence of these ionization rates on the electric field is determined analytically and a correction to Chynoweth's law is found. In this paper we merely want to show that the field dependence of the ionization rates given by Chynoweth's law (αsc = αsc exp(-bsc/E) with s = {n, p}) is, in general, a crude approximation within our more general theory. Rather we shall derive an approximation of the following form: α s = a s z exp − b s E(x) with z(x) = 1 + b n E(x) exp − b p E(x) and a s = 1 L s , b s = U s c qL s , s ={n, p} We want to stress that the purpose of our paper is not to determine the physical parameters, as, bs from multiplication factor measurements. Rather we want to convince the reader that our expression of the ionization rate is both a simple and, for narrow junctions, a necessary correction to Chynoweth's law. Considering abrupt p-n junctions with different doping concentrations it is shown that our dependence of ionization rate on electric field E(x) is valid in a range 2 × 105 The arguments used are self contained.
TL;DR: In this article, the sheet resistance of the internal base of a bipolar transistor tetrode with two separated base contacts is measured and the interrelation between rsi and the total hole charge can be determined experimentally.
Abstract: A comparatively simple method is described which allows to measure the sheet resistance rsi of the internal base even for a strong injecting emitter (strong “forward-bias condition”). For this, a well-known bipolar transistor tetrode with two separated base contacts is used. In order to extend the admissible operating range to sufficiently high collector current densities, corrections of the directly measured (voltage and current modulated) sheet resistance are required, which eliminate the error caused by emitter current crowding and emitter edge effects. For this, analytical correction terms are derived by solving a simplified differential equation for the internal base region. Moreover, the interrelation between rsi and the total hole charge of the internal transistor (which can be determined experimentally) can be used to extend the admissible current density range further. The proposed method was verified by numerical device simulations and, in addition, applied to experimental rsi determination. It proved to be well suited up to very high collector current densities, where rsi is considerably reduced compared to its zero-bias or even weak-injection value.
TL;DR: In this paper, the authors used the time resolved microwave (TRMC) method to characterize single crystalline silicon wafers with a contactless, nondestructive transient photoconductivity method.
Abstract: The possibilities and limitations of characterizing single crystalline silicon wafers with a contactless, nondestructive transient photoconductivity method, i.e. the time resolved microwave (TRMC) method has been demonstrated. The bulk lifetime and the diffusion constant of minority charge carriers in n - and p -doped silicon wafers (ρ: 1–200 Ω cm) were determined in two different ways: by varying the wafer thickness and by changing the surface recombination velocity via different etching treatments. Using electron irradiated (14 MeV) wafers, it was shown that this method can be used for the detection of changes in the bulk lifetime.
TL;DR: In this paper, low-frequency (LF) measurements were performed on aluminum thin films biased at current densities of 5 × 10 5 to 3 × 10 6 A/cm 2 at different temperatures up to 200°C.
Abstract: Low-frequency (LF) noise measurements were performed on aluminum thin films biased at current densities of 5 × 10 5 to 3 × 10 6 A/cm 2 at different temperatures up to 200°C. Correlation between the mechanisms causing these LF fluctuations and electromigration was investigated. Contrary to the 1/ f 2 form observed by other researchers, we observed 1/ f γ noise spectra where γ varied between 0.8 and 1.5. Through the Arrhenius plot of noise power spectral density, activation energies ranging from 0.60 to 0.69 eV have been obtained which agree with activation energies obtained through 1/ f 2 noise measurements. These values also agree with activation energies measured by conventional stressing techniques and are in the same range as electromigration mechanisms originating from grain boundaries. Through the current dependence of γ, and the current dependence of the noise power magnitude, we attempted to predict electromigration damage and time-to-failure. For the first time, we incorporated the current dependence of the spectral form in the analysis of noise magnitude for electromigration.
TL;DR: In this article, the conduction properties of CrSiO2Si capacitors were investigated and process dependent excess currents of a Fowler-Nordheim type correlated with the breakdown strength were shown to exist at low field.
Abstract: The conduction properties of CrSiO2Si capacitors are investigated. Process dependent excess currents of a Fowler-Nordheim type correlated with the breakdown strength are shown to exist at low field. These currents have characteristics different from those of known high field induced excess currents.
TL;DR: In this paper, numerical simulations of GaAs MESFETs with deep chromium acceptors in the semi-insulating substrate were made, and the results were compared with those obtained for a case with deep donors such as EL2 centers and shallow acceptors.
Abstract: Numerical simulations of GaAs MESFETs with deep chromium acceptors in the semi-insulating substrate were made. The results were compared with those obtained for a case with deep donors such as EL2 centers and shallow acceptors. It was found that an acceptor density in the substrate is a predominant factor in determining current-voltage characteristics of GaAs MESFETs, whether the acceptor is deep or shallow. Potential profiles were, however, found to depend strongly on the nature of deep levels in the substrate, suggesting that different drain breakdown characteristics or different backgating effects may be observed between the two cases. To minimize short-channel effects in GaAs MESFETs, the substrate conduction must be reduced. For this purpose, the deep-acceptor density in the semi-insulating substrate should be made high.
TL;DR: In this paper, a metal-insulator-InP diodes with Al, Ni, Au and Pd Schottky contacts were fabricated using improved surface passivation techniques, and the currentvoltage characteristics and the barrier height data indicate that a thin layer of thermal oxide between the metal-inP interface and a proximity cap protection during the RTA ohmic contact annealing improve the surface properties, as confirmed by deep level transient spectroscopy (DLTS), no surface trap being detected.
Abstract: Metal-insulator-InP diodes with Al, Ni, Au and Pd Schottky contacts were fabricated using improved surface passivation techniques. The current-voltage (I–V) characteristics and the barrier height data indicate that a thin layer of thermal oxide between the metal-InP interface and a proximity cap protection during the RTA ohmic contact annealing improve the surface properties, as confirmed by deep level transient spectroscopy (DLTS), no surface trap being detected. The chemical reactivity of the metal with oxide and n-InP is important to the formation of Schottky barriers. The reactive metals Al and Ni gave a low barrier height due to the reduction of oxide and reaction with InP. Nonreactive metals Au and Pd gave a high barrier height. The modified thermionic emission (TE) theory and thermionic field emission (TFE) theory can be used to explain the conduction mechanisms on Ni and Au MIS diodes. The Pd MIS diode exhibited an excess current component at low forward bias due to surface states which predominate at low temperature.
TL;DR: The drain voltage noise of commercial AlGaAs/GaAs HEMTs shows typical ƒ −1.0 noise characteristics with a Hooge noise parameter of about 6 × 10−5, while that of conventional GaAs MESFETs has a large GR noise bulge at about 15 Hz.
Abstract: The drain voltage noise of commercial AlGaAs/GaAs HEMTs shows typical ƒ −1.0 noise characteristics with a Hooge noise parameter of about 6 × 10−5, while that of conventional GaAs MESFETs has a large GR noise bulge at about 15 Hz. The noise levels of the HEMT are smaller than those of the MESFET by 19 dB Hz−0.5 at the same bias conditions, manifesting the advantage of HEMT as a low-noise device.
TL;DR: In this paper, the electron mobility fluctuations due to scattering from vacancies migrating along the grain boundaries are used to explain the shape of the experimentally observed low-frequency spectra, the current dependence of the noise magnitude and the frequency exponent γ, as well as the temperature dependence of γ can be accurately explained.
Abstract: At stressing-current densities, low-frequency noise in thin-metal films has been known to have a 1/ƒγ component where γ is between 0.8 and 2. Although several experimental investigations have been made to measure electromigration parameters such as activation energy and lifetimes of metallization layers by low-frequency measurements, investigators so far have had to rely upon semi-empirical expressions for theory. In this paper we develop a theory connecting ion migration in metals to low-frequency noise. The model is based on the electron mobility fluctuations due to scattering from vacancies migrating along the grain boundaries. Through this model the shape of the experimentally observed low-frequency spectra, the current dependence of the noise magnitude and the frequency exponent γ, as well as the temperature dependence of γ can be accurately explained. Moreover, the model also yields the observed thermally activated form and the activation energies for the low-frequency noise magnitude.
TL;DR: In this paper, the effect of different bias circuit elements on the measured d.c. I − V curves of a double-barrier diode was studied with experimental and theoretical results.
Abstract: Bias circuit stability has important implications for the study and application of double-barrier resonant tunneling structures. Stability criteria for resonant tunneling diodes are investigated for the common bias circuit topologies. A systematic study was made of the effect of different bias circuit elements on the measured d.c. I − V curves. A double-barrier diode was studied as an example, with experimental and theoretical results. The main results of the paper are (1) stable resonant tunneling diode operation is difficult to obtain, (2) the low-frequency oscillation introduces a characteristic signature in the measured d.c. I − V characteristic.
TL;DR: In this article, the collector-emitter offset voltage in heterojunction bipolar transistors is studied in detail based on an in-depth analysis of junction characteristics at zero collector current.
Abstract: Collector-emitter offset voltage in heterojunction bipolar transistors is studied in detail. Based on an in-depth analysis of junction characteristics at zero collector current, a general model for offset voltage applicable to homojunction, single heterojunction and double heterojunction bipolar transistors is obtained. For an abrupt SHBT, the conduction band discontinuity at emitter-base heterojunction is found to be the main cause of large offset voltages. For DHBT's it is found that even when emitter and collector base junctions are identical in all respects, they will have an offset voltage with a magnitude dependent on the current gain of the transistor. Appropriate grading of emitter-base junction is shown to reduce the offset voltage in HBT's to values obtained in homojunction bipolar transistors.
TL;DR: An analytical solution for the minority carrier concentration to the 2-D diffusion equation in the base of a mesa-structure bipolar transistor is derived in this paper, which is especially applicable for AlGaAs/GaAs heterojunction bipolar transistors for which the extrinsic base surface has a high surface recombination velocity if the surface is not passivated.
Abstract: An analytical solution for the minority carrier concentration to the 2-D diffusion equation in the base of a mesa-structure bipolar transistor is derived. The solution is especially applicable for AlGaAs/GaAs heterojunction bipolar transistors for which the extrinsic base surface has a high surface recombination velocity if the surface is not passivated. The different components of the base current are determined from the derived 2-D minority carrier concentration in the base. The major components to the base current include: surface recombination at the extrinsic base surface, at the base ohmic contact and bulk recombination in the base. The relative importance of each component is discussed as a function of the extrinsic base length, emitter length and base doping. The effects of quasielectric field in the base and the passivation on the extrinsic base region are also evaluated. The results indicate that as base doping is increased, the current gain is limited by bulk recombination, independent of the details of the device geometry.
TL;DR: In this article, the authors compared the hydrodynamic model and a simple, efficient energy transport model to evaluate their performance under submicron device conditions, and to better assess how they may be improved.
Abstract: The reduction in feature size of silicon devices has resulted in operating conditions characterized by extremely large internal electric fields and field gradients. The rapid spatial variation of the electric field precludes a point-wise (or local) dependence of average carrier energy on the electric field. Because traditional drift-diffusion transport models and field-dependent hot-carrier models force a one-to-one correspondence between the local electric field and carrier energy, they fail to provide sufficient accuracy for contemporary device design. Impact ionization in submicron MOSFETs, for example, is poorly described by field-dependent ionization coefficients since impact ionization is an energy-dependent process. Energy transport models, which can account for the nonlocal energy-field relationship in submicron devices, have become especially attractive for design oriented silicon device simulation. The severe constraints that hot (high energy) carriers impose on current submicron MOSFET technology have motivated the development and application of energy transport models, such as the hydrodynamic model. In this work, the hydrodynamic model and a simple, efficient energy transport model are compared with a Monte Carlo model in order to evaluate their performance under submicron device conditions, and to better assess how they may be improved. The results indicate that energy transport models can predict peak average energy quite well, even under severely nonuniform electric field conditions. The hydrodynamic and simple energy transported models examined here, however, cannot accurately model carrier cooling associated with an abrupt decrease in the electric field. Discrepancies in cooling are shown to strongly influence drift velocity, and the implications of this for submicron device analysis are discussed.
TL;DR: In this article, an analytical model for extraction of the spatial trapped charge density in silicon nitride has been formulated with amphoteric trap statistics, including the energy distribution of traps in nitride and the time-dispersive tunneling transitions from these nitride traps.
Abstract: In this paper an analytical model for extraction of the spatial trapped charge density in silicon nitride has been formulated with amphoteric trap statistics. The model includes the energy distribution of traps in nitride and the time-dispersive tunneling transitions from these nitride traps. We have examined charge loss from sub-100 A nitride films with MONOS memory devices at 110 K at different gate bias conditions. We conclude that by maintaining depletion/weak-inversion at the Si surface, the primary charge loss mechanism is back-tunneling of charge from the nitride traps into the Si bands. The actual charge distribution in the nitride is a function of charge injection and trapping. We have demonstrated that modified Fowler-Nordheim tunneling of electrons into the nitride generates a non-uniform spatial distribution of trapped charge for a spatially uniform trap density in the nitride.
TL;DR: In this paper, the Schottky barrier heights of the MBE-grown diodes were measured by both the current-voltage (I-V), φBIV and capacitance-voltages (C-V) methods, with φBCV larger by 47±10 meV in all the Diodes.
Abstract: Factors contributing to Schottky barrier lowering in ideal Al/GaAs Schottky diodes are discussed both theoretically and experimentally. The diodes used in this study were grown by molecular beam epitaxy with in situ Al deposition. Two different GaAs surface reconstructions (As-stabilized and Ga-rich) were used. The Schottky barrier heights of these diodes were measured by both the current-voltage (I-V), φBIV and capacitance-voltage (C-V), φBCV, methods, with φBCV larger by 47±10 meV in all the diodes. The barrier lowering effects observed in the I-V measurements are consistent with the measured ideality factor of 1.03±0.01. The experimental results coincide closely with theoretical values when the barrier lowering effects due to quantum mechanical tunneling calculated by the transfer matrix technique and image force are included. These two barrier lowering effects result in the observed larger than unity ideality factor. Simulations show that barrier lowering due to image force is reduced when tunneling occurs. The use of the effective mass approximation as opposed to the k·p method in obtaining the complex wave-vectors of the electrons does not lead to any significant change in the results. In view of these findings, the MBE grown diodes reported here are the closest to ideal ever reported in the literature.
TL;DR: A diamond p − n junction diode has been fabricated by the chemical vapour deposition technique as mentioned in this paper, which shows distinct rectification characteristics at 300 K room temperature and this result implies the possible use of diamond as a semiconductor in high temperature conditions.
Abstract: A diamond p − n junction diode has been fabricated by the chemical vapour deposition technique. Diphosphorus pentaoxide and boron trioxide were used for the doping sources for the n - and p -type layers, respectively. The diode shows distinct rectification characteristics at 300 K room temperature. This diode shows rectification even at 370 K and this result implies the possible use of diamond as a semiconductor in high temperature conditions.
TL;DR: In this article, a numerically intensive model of a silicon solar cell with an optimization algorithm is developed, and it is demonstrated that the computational burden of evaluating the optimal design of a solar cell can be significantly decreased if the model is appropriately adapted for use in an optimization environment.
Abstract: The coupling of a numerically intensive model of a silicon solar cell with an optimization algorithm is developed. It is demonstrated that the computational burden of evaluating the optimal design of a solar cell can be significantly decreased if the model is appropriately adapted for use in an optimization environment. It is shown that the resulting tool is extremely useful for performing a systematic analysis of optimal efficiencies and associated optimal designs under different levels of technology and fabrication processes. The paper also demonstrates that true sensitivity analyses can be carried out only in an optimization context.
TL;DR: In this paper, the field-dependent tunnel-generation rate in GaAs has been experimentally determined from reverse-bias current measurements of MBE made submicron pin-structures.
Abstract: The field-dependent tunnel-generation rate in GaAs has been experimentally determined from reverse-bias current measurements of MBE made submicron pin-structures. The obtained results, tunneling rate and temperature coefficient, agree well with theoretical calculations.