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Electron Devices, IEEE Transactions on

Issue 5 • Date May 1987

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Displaying Results 1 - 25 of 45
  • [Front cover and table of contents]

    Page(s): c1
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    Freely Available from IEEE
  • Threshold field and peak-valley velocity ratio in short samples of InP at 300 K

    Page(s): 953 - 956
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    The transient and steady-state velocity-field characteristics of InP at 300 K are calculated for short samples by using a Monte Carlo model. It is found that the threshold field for negative differential resistance increases with a decrease in the sample length, but the peak-valley velocity ratio is almost independent of the sample length. View full abstract»

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  • Degradation mechanism of Ti/Au and Ti/Pd/Au gate metallizations in GaAs MESFET's

    Page(s): 957 - 960
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    Modifications of several dc parameters of GaAs MESFET's induced by accelerated aging at 300 °C have been investigated in a test pattern configuration. Two different gate metallization structures have been examined, namely GaAs/Ti/Au and GaAs/Ti/Pd/Au. The gate diode and the MESFET characteristics of the former degrade noticeably upon annealing, while they are less affected by the thermal treatments for the latter. This different behavior is probably induced by the formation of different compounds at the metal-GaAs interface, which modify the gate diode properties. View full abstract»

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  • Electrical switching speed of the double-heterostructure optoelectronic switch

    Page(s): 961 - 965
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    The electrical switching speed of a new double-heterostructure optoelectronic switch (designated DOES) is measured in a relaxation oscillator circuit. A minimum value of capacitance was required to obtain oscillations. The turn-on speed was measured to be 100 ps. The turn-off speed was limited to the RC pull-up time. View full abstract»

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  • A potentially low-noise avalanche diode microwave amplifier

    Page(s): 966 - 972
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    A sequence of AlGaAs, GaAs heterojunctions can be used to generate a series of potential steps that are just large enough to accelerate conduction-band electrons to energies above the impact-ionization threshold while valence-band holes do not obtain this much energy. The smaller difference in the valence-band heterojunction discontinuity and the higher scattering rate for holes than conduction-band electrons are shown to suppress the initiation of impact ionization by valence-band holes in this structure. The resulting transit-time device is predicted to be a relatively low-noise amplifier or oscillator that can be used in the microwave region and will be insensitive to small fluctuations in the power supply voltage. View full abstract»

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  • Theory of electron conduction in the double-heterostructure optoelectronic switch (DOES)

    Page(s): 973 - 984
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    In this paper a theory is developed for the double heterostructure optoelectronic switching device (DOES). The DOES is a new optoelectronic device in which the optical output can be switched with either an electrical or an optical input. It may be regarded as an LED or laser that has been combined internally with an electrical switching device. The device may be triggered from its OFF-state (high impedance and no emission) either optically or electrically into its ON-state where it emits light and exhibits low impedance. The device therefore has binary electrical states and binary optical states that may be changed by either an electrical or an optical input, or combinations thereof. View full abstract»

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  • Quasi-two-dimensional modeling of GaAs MESFET's

    Page(s): 985 - 991
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    A numerical simulation of GaAs MESFET structures is presented. The approach taken in this paper combines an analytical solution with a full simulation. Poisson's equation, the current continuity equation, and an electron-temperature equation are formulated in terms of a geometry factor that defines the shape of the conducting channel in the MESFET. The transport equations are then solved in one dimension and the channel geometry factor is found analytically. This method was found to be considerably faster than full two-dimensional simulations. The model has been compared to full two-dimensional drift-diffusion and energy-momentum results to determine its validity. View full abstract»

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  • Theoretical analysis of the layer design of inverted single-channel heterostructure transistors

    Page(s): 992 - 1000
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    In this paper the inverted heterostructure transistor is analyzed using a self-consistent model for calculation of the electron concentration and spatial distribution in the quantum well. The (In,Ga)As/(Al,Ga) As material system is considered in particular. The objective of the study is to design a transistor with a high channel electron concentration and a short gate-to-channel distance. It furthermore is desired that the channel concentration can be selected without influence from the gate-to-channel distance. Placing the gate close to the channel means that the leakage current may become unacceptably high. The analysis therefore includes an estimate of the leakage current that can be expected for each structure. It is shown that the best way of meeting the design objectives is to use a material between the channel and the gate, which consists of two layers with low- and high-bandgap materials, respectively. The structure will thus consist of a potential well with the electron accumulation occurring at the lower interface. The lower high-bandgap material furthermore should be doped as high as possible. The upper limit for the doping level in the topmost layer is determined by the maximum acceptable gate leakage as well as by gate-drain breakdown. (The latter also being partly determined by the device contact geometry.) Governed by the restrictions imposed by the application of the transistor, the model can thus be used to optimize the layer design for, e.g., minimum noise figures. View full abstract»

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  • GaAs MESFET interface considerations

    Page(s): 1001 - 1007
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    Various properties of GaAs MESFET's are discussed in terms of the basic physics of interfaces and deep levels. Fermi-level pinning is shown to lead to hole injection from a positively biased metal lying in direct contact with semi-insulating GaAs. This hole injection is partially responsible for low-frequency oscillations in GaAs MESFET's. Backgating and low-frequency oscillations are shown to be a direct consequence of the peculiar nature of the channel-substrate interface. This interface is discussed within the framework of a three-level model. View full abstract»

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  • Two-dimensional thermal oxidation of silicon—I. Experiments

    Page(s): 1008 - 1017
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    With continued miniaturization and the development of new devices, the highly nonuniform oxidation of two-dimensional non-planar silicon structures is playing an increasingly important role. An understanding of this subject has been limited by insufficient experimental data and difficulties in two-dimensional numerical simulation. This paper introduces a unique experimental approach in which extensive data were obtained concerning the oxidation of cylindrical silicon structures of controlled radii of curvature. It is quantitatively demonstrated that the oxidation of curved silicon surfaces is retarded at low temperatures and sharp curvatures, and that the retardation is more severe on concave than convex structures. These observations will be interpreted using a physical model based on stress effects on oxide growth parameters. The theoretical analysis and modeling will be reported in detail in a separate paper [1]. View full abstract»

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  • Metallization by ionized cluster beam deposition

    Page(s): 1018 - 1025
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    Preferentially oriented and epitaxial Al films have been deposited by ionized cluster beams (ICB). The thermal stability of these films has been examined by SEM, AES, ion backscattering, and electrical characterization. In preferentially oriented films, long electromigration lifetime and low-temperature contact formation are expected. In epitaxial films on silicon, alloy penetration at the interface, a shift in barrier height, and degradation of crystalline quality were not observed after heat treatment up to 550 °C. Extremely long electromigration lifetime was also confirmed. Epitaxial growth Of Al film on CaF2, GaAs, and sapphire was attempted and preliminary results are given. View full abstract»

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  • Sputtered Ni-P as an ohmic contact to n-InP, p-InGaAs and as a diffusion barrier

    Page(s): 1026 - 1032
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    Ni2P is a metallic conductor with a bulk resistivity of 32 µΩ . cm. Films of Ni2P can be sputter-deposited in both the amorphous and crystalline forms by varying the sputtering parameters. The amorphous to crystalline transition has been found to take place at about 250 °C and sufficient grain growth to exhibit X-ray reflections takes place by 400 °C. In both forms, films of Ni2P have been found to form ohmic contacts to n-InP (Sn doped 2 × 1018cm-3) p-InGaAs (Zn-doped 8 × 1018cm-3) with sufficiently low sheet resistivity and specific contact resistance to be useful as a metallization layer in most devices. It was also found that up to 400 °C, amorphous (as sputtered) films of Ni2P function as efficient diffusion barriers between an outer Au layer and the III-V substrate. It is possible, therefore, for amorphous (as sputtered) films of Ni2P to function simultaneously both as a metallization layer and diffusion barrier. View full abstract»

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  • A new analytical model of the "Bird's beak"

    Page(s): 1033 - 1038
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    The numerical simulation of technological processes is very important for the fabrication of integrated circuits. The authors have developed the two-dimensional simulator OSIRIS allowing the simulation of ion implantation and redistribution of dopants in silicon. An original analytical model for oxide growth has been developed that gives very good simulation of the "bird's beak" of SEMIROX structures. As an example, a complete simulation of an n-channel MOS device is presented with the redistribution impurity profiles and the oxide layer shape at the end of the process. View full abstract»

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  • Development of a new self-aligning contact technology

    Page(s): 1039 - 1045
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    A self-aligning contact process (SACMOS) for MOS/VLSI technology is described. A new technique involving submerged implant into the source and drain is employed. This enables the enhanced oxidation of the previously heavily doped polysilicon gate compared to the more lightly doped source and drain. The implant also provides the source and drain extensions. During oxidation, silicon nitride pads protect all contacts. A noncritical masking and etching stage is used to yield contacts. The process uses two extra masking stages to produce self-aligned contacts to the source, drain, and gate of MOS transistors, yielding a significant reduction in the area required for contact regions and hence a greater packing density. A process verification chip illustrated that discrete transistors designed using the new process exhibited similar properties to conventionally designed devices. Also a 21-stage ring oscillator designed with a minimum dimension of 6 µm occupied 15 percent less space than a conventional device and operated at the same speed under similar bias conditions. Finally it is estimated that a ROM designed using the new process occupies 25 percent less space. View full abstract»

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  • Millimeter-wave bulk unipolar mixer diodes

    Page(s): 1046 - 1051
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    The use of a bulk unipolar camel diode as a mixing element is considered. A diode of this type is shown to have a conversion loss of between 7 and 8 dB over the frequency range 27 to 35 GHz, with a similar SSB noise figure. View full abstract»

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  • Smear reduction in the interline CCD image sensor

    Page(s): 1052 - 1056
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    An undesirable smear in a vertical-overflow-drain interline CCD image sensor (VOD IL-CCD) has been analyzed. This smear has been reduced by using a new structure. The main cause of the smear was identified, using an experimental linear CCD image sensor, as light leakage, i.e., oblique incident light effect, concave lens effect, diffraction effect, and waveguide effect, To reduce the light-leakage smear, a new structure is proposed, where the oxide thickness under the aluminum photoshield is as small as 0.2 µm. As a result, the photoshielding performance is improved, and the smear-to-signal ratio for 10-percent vertical height illumination in the new structure VOD IL-CCD obtained is 0.016 percent, or 12 times smaller than that in a conventional structure VOD IL-CCD. View full abstract»

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  • Surface-depleted photoconductors

    Page(s): 1057 - 1060
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    Photoconductors with channels that lie in the surface depleted region of a GaAs epitaxial structure are described. These devices have microampere photocurrent at saturation conditions under 0.3 mW illumination and exhibit photoconductive gain. The dark current is in the nanoampere range and the noise equivalent power is of the order of 10-12W/√Hz. In contrast to other photoconductors, their low frequency responsivity is of the same order as that in the GHz region, alleviating problems of equalization necessary in receiver applications. As well, these devices exhibit over 60 dB isolation and sub-nanosecond switching time as optoelectronic switches. View full abstract»

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  • BJT—MOSFET transconductance comparisons

    Page(s): 1061 - 1065
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    Through normalization it becomes possible to construct curves of considerable generality for comparing the transconductance properties of BJT's and MOSFET's. Three comparisons are given. The first presents transconductance as a function of output current; the second, transconductance divided by output current as a function of input voltage; and the third, transconductance as a function of input voltage. The BJT advantage increases rapidly with output current and (or) input voltage. The curves approach each other under extremely low-level conditions, but appreciable deviations from the simple theory upon which the present analysis is based also occur in the low-level regime--especially deviations connected with subthreshold conduction in the MOSFET, as well as "excess" conduction near but above threshold. For these reasons, the moderate-level portions of the simple-theory comparisons are the most meaningful. Recently developed subthreshold analysis is also used in the second comparison. View full abstract»

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  • A study of channel avalanche breakdown in scaled n-MOSFET's

    Page(s): 1066 - 1073
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    The behavior of channel avalanche breakdown in n-MOSFET's miniaturized by isothermal constant field scaling is examined. Both a first-order analytical estimate and a rigorous two-dimensional numerical simulation of electrically wide devices are used to understand the scaling of channel breakdown. A sublinear dependence of snapback and sustaining voltages on channel length is found and explained. In practical terms, this sublinear dependence means that the relative MOS channel breakdown behavior improves for scaled-down devices. The breakdown behavior was verified against experimental data taken on a 1.3-µm n-channel device. In addition, a model is proposed for channel breakdown on unscaled devices that differ only in channel length. View full abstract»

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  • MINIMOS 3: A MOSFET simulator that includes energy balance

    Page(s): 1074 - 1078
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    We present a model for hot carrier transport which is implemented in the device simulator MINIMOS 3. A brief resume of the model is given. We present various results which were calculated with this new model. We show that the I-V characteristics of a MOSFET can be calculated from Leff= 10 µm down to Leff= 0.9 µm with one parameter set. Modifications of carrier and current distributions are presented that show how hot carrier effects tend to smooth these distributions. Implications are discussed how a self-consistent carrier temperature can be used to model impact ionization and oxide injection. View full abstract»

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  • Hot-carrier effects in Hydrogen-passivated p-channel polycrystalline-Si MOSFET's

    Page(s): 1079 - 1083
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    The dependence of hot-carrier effects on channel length and stress-bias voltage in hydrogen-passivated accumulation-mode p-channel polycrystalline-Si MOSFET's operating in the saturation region has been studied, Before stress, these devices exhibit a minimum value of current at VGS≈ 0 V but as VGSincreases above 0 V, they show an increase in (leakage) current due to field-enhanced generation of carriers near the drain. After stress, the current at VGS≈ 0 V increases slightly with respect to its pre-stress value. However, the current then monotonically decreases as VGSincreases above 0 V unlike the situation before stress. No change in reverse mode (source and drain reversed) characteristics and no change in the ON-state (VGS< 0 V) forward-mode characteristic was observed after stress. These observations are shown to be due to hot-carrier-induced acceptor-type interface states near the drain in forward-mode operation. View full abstract»

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  • A 90-GHz double-drift IMPATT diode made with Si MBE

    Page(s): 1084 - 1089
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    For the first time silicon double-drift IMPATT structures have been grown completely by Si molecular-beam epitaxy. The n-type layers are grown at 750 °C on low-resistivity n+-type substrates followed by p-type layers at 650 °C. The highly doped p+-layers are grown by solid-phase epitaxy in the MBE system. Device design is made for CW operation in W-band. The material is investigated by inspection of beveled samples, defect etching, TEM, SIMS, and spreading resistance measurements. Double-drift flat-profile diodes are housed and mounted employing a technological procedure approved for single-drift diodes. For initial device characterization, dc measurements are performed. Information about doping profile, series, and thermal resistances is obtained. Preliminary RF measurements delivered a maximum output power of 600 mW at 94 GHz with 6.7-percent efficiency from an unoptimized structure. View full abstract»

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  • The transient integral charge control relation—A novel formulation of the currents in a bipolar transistor

    Page(s): 1090 - 1099
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    The present paper describes the transient integral charge control (TICC) relation. This term designates a formula describing the emitter, base, and collector terminal currents of a bipolar junction transistor (BJT) for a one-dimensional current flow. The relation holds for dc as well as for transient bias conditions, and basically can be regarded as a more general formulation of Gummel's charge control relation [1], whose validity is restricted to dc conditions and to situations where recombination and generation effects are negligible. The structure of the TICC relation resembles Gummel's formulation extended by some additional terms. We shall use this relation in order to derive a formula for the high-frequency behavior of the transconductance. The expression obtained via the TICC relation allows for physical interpretation and simple calculation. The validity of the derived formulas is carefully checked by numerical means. This yields a validity range of our approach far beyond the Start of the high-current regime. View full abstract»

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  • Flicker (1/f) noise generated by a random walk of electrons in interfaces

    Page(s): 1100 - 1115
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    Flicker noise can be generated by a random walk of mobile electrons in interfaces via interface states. It is proposed that these electrons interact with surface phonons to form polarons, which have very low mobilities. The flicker-noise model is a general one and may be used to explain flicker noise on MOSFET's, clean Si surfaces, metallic resistors, grain boundaries, amorphous layers, electron tubes, metal-insulator-metal junctions, diodes, and transistors. The dependence of the noise intensity is calculated as a function of device parameters such as interface state density, source-drain current, source-drain voltage, gate voltage, oxide layer thickness, grain size, temperature, size of the cathode, diode current, base current, and the surface recombination in the emitter-base area. Hooge's parameter is calculated quantitatively for several devices. View full abstract»

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  • "Soft" energy thresholds in impact ionization: A classical model

    Page(s): 1116 - 1120
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    A new simplified approach to the problem of "soft" threshold energy in impact ionization in semiconductors is presented. The model used is entirely classical and leads to a simple exact formula for the ionization rate as a function of energy. This result is used as the basis for modifying the "lucky drift" model of impact ionization, as has been done previously for other models of the "soft" threshold. The final analytic relations show excellent agreement with the available experimental data for the ionization coefficients in GaAs but indicate that the impact ionization process may involve three (or more) incident particles rather than two as previously thought. View full abstract»

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IEEE Transactions on Electron Devices publishes original and significant contributions relating to the theory, modeling, design, performance and reliability of electron and ion integrated circuit devices and interconnects.

 

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Editor-in-Chief
John D. Cressler
School of Electrical and Computer Engineering
Georgia Institute of Technology