Showing papers on "Doping published in 1988"

Monte carlo analysis of electron transport in small semiconductor devices including band-structure and space-charge effects

Abstract: The physics of electron transport in Si and GaAs is investigated with use of a Monte Carlo technique which improves the "state-of-the-art" treatment of high-energy carrier dynamics. (1) The semiconductor is modeled beyond the effective-mass approximation by using the band structure obtained from empirical-pseudopotential calculations. (2) The electron-phonon, electron-impurity, and electron-electron scattering rates are computed in a way consistent with the full band structure of the solid, thus accounting for density-of-states and matrix-element effects more accurately than previous transport formulations. (3) The long-range carrier-carrier interaction and space-charge effects are included by coupling the Monte Carlo simulation to a self-consistent two-dimensional Poisson solution updated at a frequency large enough to resolve the plasma oscillations in highly doped regions. The technique is employed to study experimental submicrometer Si field-effect transistors with channel lengths as small as 60 nm operating at 77 and 300 K. Velocity overshoot and highly nonlocal, off-equilibrium phenomena are investigated together with the role of electron-electron interaction in these ultrasmall structures. In the systems considered, the inclusion of the full band structure has the effect of reducing the amount of velocity overshoot via electron transfer to upper conduction valleys, particularly at large biases and low temperatures. The reasonableness of the physical picture is supported by the close agreement of the results of the simulation to available experimental data.

Band-gap tailoring of ZnO by means of heavy Al doping

Abstract: Films of ZnO:Al were produced by weakly reactive dual-target magnetron sputtering. Optical band gaps, evaluated from spectrophotometric data, were widened in proportion to the Al doping. The widening could be quantitatively reconciled with an effective-mass model for n-doped semiconductors, provided the polar character of ZnO was accounted for.

New semiconductor device physics in polymer diodes and transistors

Abstract: Semiconductor devices have been made from polyacetylene, a conjugated polymeric semiconductor. The device operates in a novel way: charge is stored in localized soliton-like excitations of the polymer chain, which are introduced not by doping or photoexcitation but by the presence of a surface electric field. The formation of charged solitons changes the optical properties of the polymer, introducing optical absorption below the band gap. Combined with the processibility of the polymer, these new electro-optic effects may be exploited technologically in electro-optic modulators.

The physics and technology of amorphous SiO[2]

Abstract: Structure: Theory and Experiment.- Current Models for Amorphous SiO2.- Structural Similarities and Dissimilarities Between SiO2 and H2O.- Geometrical Methods in the Theory of Glasses.- Low Lying Excitations in Silica.- New Methods of IR Spectroscopic Investigation of Amorphous Insulating Films.- Vibrational Studies of Amorphous SiO2.- Raman Spectra of SiO2 Fibers at High Tensile Strain.- A Comparison of the Structure of a-SiO2 Prepared by Different Routes.- NMR Studies of Neutron-Irradiated Crystalline and Vitreous SiO2.- Intrinsic and Extrinsic Defects: Theory.- Electronic Structure of Defects in Amorphous SiO2.- Electron and Hole Traps Related to ? Bonded Oxygen Vacancy Centers in SiO2.- Theory of Oxygen-Vacancy Defects in Silicon Dioxide.- Total Energy Calculations for Intrinsic Defects in Amorphous SiO2.- Boron Impurity Centers in Si02: a Tight Binding Consideration.- Intrinsic and Extrinsic Defects: Experiment.- Intrinsic and Extrinsic Point Defects in a-SiO2.- Self-Trapped Excitons in Amorphous and Crystalline SiO2.- Identification of Native Defects in a-SiO2.- UV and VUV Optical Absorption due to Intrinsic and Laser Induced Defects in Synthetic Silica Fibers.- Incommensurate Phase of Quartz: Microscopic Origin and Interaction with Defects.- Gamma Ray Induced 2 eV Optical Absorption Band in Pure Silica Core Fibers.- On the Decay of X-Ray Induced Luminescence of SiO2.- On the Role of O-2 in the Luminescence of Amorphous and Crystalline SiO2.- Transformation of Radiation Induced Defect Centers as a Probe of Molecular Diffusion in a-SiO2.- Observation of the Neutral Oxygen Vacancy in Silicon Dioxide.- New Insight Into the Structure of SiO2 Glass from a Point Defect Study.- Hydrogen Bonds Between Peroxy Radicals and Hydrogen Molecules in SiO2 Glass.- ESR Studies of111< Si/SiO2 Interface.- Structure and Hyperfine Interaction of Si ? Si* Defect Clusters.- On the Relationship Between Thermal Growth and Thickness Inhomogeneities in Very Thin SiO2 Films.- The Pb Center at the Si-SiO2 Precipitate Interfaces in Buried Oxide Materials: 29Si Hyperfine Interactions and Linewidths.- Metastable and Multiply-Charged Individual Defects at the Si:SiO2 Interface.- The Influence of Disorder on the Si2p XPS Lineshape at the Si-SiO2 Interface.- Si-SiO2 Interfaces - a HRTEM Study.- Electrical and Interface Properties of MOS Structures of Getter Treated Silicon.- Influence of Different Preparation Methods on Interfacial (Si/SiO2) Parameters of Very Thin Layers.- Oxidation, Oxynitrides And Deposited Films.- Thermal Oxidation of Silicon.- A Framework for Incorporating Memory Effects of Structural Relaxation in Models for Thermal Oxidation of Silicon.- Analysis of Stress Relaxation and Growth Kinetics for Two-Step Thermal Oxidation of Silicon.- Photo-Induced Oxidation Processes in Silicon.- Growth and Structure of Argon Laser Grown SiO2.- Transport Properties of Plasma Enhanced CVD Silicon Oxynitride Films.- Characteristics of SiO2 and SiOxNy Obtained by Rapid Thermal Processes.- Evidence for Oxygen Bubbles in Fluorine Doped Amorphous Silicon Dioxide Thin Films.- Low Temperature PECVD Silicon Rich Silicon Dioxide Films Doped With Fluorine.- Transport, Trapping and Breakdown.- High Field Transport in SiO2.- Hot Electrons in SiO2: Ballistic and Steady State Transport.- Electronic Charge Transport in Thin SiO2 Films.- The Role of Hole Traps in the Degradation of Thermally Grown SiO2 Layers.- The Influence of Temperature Nitrogen Annealing on the Electrical Properties of Plasma Nitrided Oxides.- High-Field Positive-Charge Generation and Its Relation to Breakdown in a-SiO2.- Breakdown Mechanisms of Thermally Grown Silicon Dioxide at High Electric Fields.- Field Dependence of Time to Breakdown Distribution of Thin Oxides.- Radiation Effects.- Radiation Effects in MOS VLSI Structures.- Relationship Between Hole Trapping and Interface State Generation in the Si/SiO2 System.- Radiation Induced Conductivity of Thin Silicon Dioxide Films on Silicon.- Interface Degradation in Short Channel MOSFETs: Comparison Between the Effects of Radiation and Hot Carrier Injection.- Buried Dielectric Layers and Novel Applications.- Synthesis of Buried Dielectric Layers in Silica by Ion Implantation.- Electrical Properties of SIMOX Material and Device.- Formation Mechanisms and Structures of Thin Buried Layers of SiO2 Fabricated Using Ion Beam Synthesis.- Low Temperature ESR Study of SIMOX Structures.- Defects in Silicon-on-Insulator Structures Formed by O+ Implantation: Their Dependence on Implantation Temperature.- Interface Properties and Recombination Mechanisms in SIMOX Structures.- Porous Silica Sol-Gel Coatings for Nd: Glass High Power Pulsed Laser Laser Uses.- Vacuum Re-Emission of Positrons from a-SiO2 Layers.- Author Index.

Critical evaluation of the status of the areas for future research regarding the wide band gap semiconductors diamond, gallium nitride and silicon carbide

Abstract: The extreme thermal and electronic properties of diamond and of silicon carbide, and the direct band gap of gallium nitride, provide multiplicative combinations of attributes which lead to the highest figures of merit for any semiconductor materials for possible use in high power, high speed, high temperature and high frequency applications. The deposition of monocrystalline diamond, at or below 1 atm total pressure and at a temperature T , has been achieved on diamond substrates; the deposited film has been polycrystalline on all other substrates but the achievement is no less significant. For electronic applications, heteroepitaxy of single-crystal films of diamond, an understanding of mechanisms of nucleation and growth, methods of impurity introduction and activation, and further device development must be achieved. Stoichiometric gallium nitride free of nitrogen vacancies has apparently not been obtained. Thus, knowledge of the defect chemistry of this material, the growth of semiconducting films on foreign substrates, and the development of insulating layers and of their low temperature deposition as well as device fabrication procedures must be achieved. By contrast, all of these problems have already been solved for silicon carbide, including the operation of a MOSFET at 923 K — the highest operating temperature ever reported for a field-effect device. However, considerable research remains to be done regarding the development of large silicon carbide substrates, of ohmic and rectifying contacts, of new types of devices, and of low temperature techniques for the deposition of insulating layers. Fugitive donor and acceptor species in unintentionally doped samples must also be identified and controlled.

Method of fabricating n-type and p-type microcrystalline semiconductor alloy material including band gap widening elements

Abstract: A method of fabricating doped microcrystalline semiconductor alloy material which includes a band gap widening element through a glow discharge deposition process by subjecting a precursor mixture which includes a diluent gas to an a.c. glow discharge in the absence of a magnetic field of sufficient strength to induce electron cyclotron resonance.

Donor-hydrogen complexes in passivated silicon.

Abstract: Several new infrared absorption bands have been discovered in hydrogen passivated silicon doped with P, As, and Sb. The frequency shift upon substitution of D for H confirms the assignment of these bands to donor-H complexes. Thermal annealing experiments, in which both the absorption due to complexes and to free carriers were measured, confirm that donor passivation is due to complex formation, and yield the stability of the complexes. Our results suggest that H is bonded to Si rather than the donor directly.

Defects in electronic materials

Abstract: This book collects papers on semiconductor materials. Topics include: oxygen precipitation formation, silicon, boron complexes in silicon, radiation-induced defects in indium antinomide, gallium arsenides, vapor phase epitaxy, gallium and indium phosphides, crystal doping, and deep level transient spectroscopies.

Si/Ge0.3Si0.7/Si heterojunction bipolar transistor made with Si molecular beam epitaxy

Abstract: GexSi1−x heterobase n‐p‐n heterojunction bipolar transistor structure has been grown completely by Si molecular beam epitaxy for the first time. A collector‐top type design was adopted. The 3000 A p‐type Ge0.3Si0.7 heterobase layer with 5×1019 cm−3 doping level was grown on an emitter layer which was an arsenic highly doped substrate (7×1019 cm−3), followed by a 5000 A n‐type Si collector layer with 7×1017 cm−3 doping level. Low‐temperature device processes under 650 °C were used to avoid thermal diffusion of impurities. Common‐emitter current gain hFE with a 100‐μm‐diam emitter was 15 at 2×104 A/cm2 collector current density. Compared with a usual Si‐base bipolar transistor of the same size and doping level, an improvement in current gain was observed. Furthermore, GexSi1−x/Si (x=0.1–0.4) p‐n junction interfaces were investigated by current‐voltage and capacitance‐voltage measurements and transmission electron microscopy observation.

Band‐gap narrowing in heavily doped silicon: A comparison of optical and electrical data

Abstract: The band‐gap narrowing in heavily doped silicon has been studied by optical techniques—namely, photoluminescence and photoluminescence excitation spectroscopy—and by electrical measurements on bipolar transistors. The optical experiments give a consistent set of data for the band‐gap narrowing in n‐ and p‐type material at low temperatures as well as at room temperature. A good agreement is found between the optical and electrical data removing the discrepancies existing so far in the literature.

Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

Abstract: Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

Thermal conductivity of heavily doped low‐pressure chemical vapor deposited polycrystalline silicon films

Abstract: The lateral thermal conductivity of heavily doped low‐pressure chemical vapor deposited polycrystalline silicon films is measured using polycrystalline silicon microbridges elevated three micrometers above a silicon substrate. The bridges, lightly doped in their central regions and heavily doped elsewhere, are fabricated using a sacrificial silicon‐dioxide layer and phosphorus out‐diffusion from doped oxide. Voltage‐current characteristics measured on the bridges both under high vacuum and in silicone oil are used to calculate lateral thermal conductivity in the polycrystalline silicon. The experimental values for the thermal conductivity of heavily doped polycrystalline silicon range from 0.29 to 0.34 W cm−1 K−1 and average 0.32 W cm−1 K−1. These values agree closely with results obtained by a second method that employs uniformly doped polycrystalline silicon bridges. In the second method, high‐vacuum, voltage‐current characteristics are measured and the indicated thermal conductivities for two samples a...

Modulation spectroscopy as a tool for electronic material characterization

Abstract: Modulation spectroscopy is an optical characterization tool that can be of great utility to the materials scientist. We present here numerous examples where a simple photo-reflectance and electroreflectance setup is used in our laboratory to determine such important material parameters as alloy composition and carrier concentration in a very short time. For determining alloy composition in semiconductors, contactless room temperature photoreflectance is nearly as sensitive as low temperature photoluminescence. Examples will be given on how to determine: the effects of surface preparation and implant damage; alloy composition and carrier homogeneity for large area wafers to better than 1%; the segregation coefficient of isoelectronic impurities in bulk semiconductors; the sub-band energies in quantum well structures; and the presence and homogeneity of built-in electric fields in MODFET structures. Particular emphasis will be placed on band edge and exciton effects on the photoreflectance and on the criteria used to distinguish between them. Materials studied included Si doped GaAs, AlxGa1-xAs for variousx grown by OMVPE and MBE, bulk InP doped with iso-electronic As and Sb, and MODFET structures.

Mechanisms of thermal equilibration in doped amorphous silicon

Abstract: Experimental and theoretical investigations of the mechanisms of thermal equilibration in n-type amorphous silicon are presented. The time, temperature, and doping dependence of the band-tail electron density is obtained from sweep-out experiments, and the dangling-bond and donor densities from photothermal deflection spectroscopy (PDS), bias annealing, and C-V characteristic measurements. An important new result is that donors participate in the equilibration, and that the doping efficiency can be greatly enhanced by a depletion bias. Numerical modeling of the transport allows us to deduce the changes in the density of states and in the position of the Fermi energy, both in equilibrium and in the frozen-in state. The equilibrium state is derived by minimizing the free energy of the doped a-Si:H using a simple density-of-states model. With this approach, the electronic properties (doping efficiency, conductivity, Fermi energy, etc.) can be computed and are shown to be in fairly good agreement with all the experimental results, although the observed lack of temperature dependence of the dangling-bond density remains a puzzle. Further evidence is presented that hydrogen motion is the underlying mechanism of equilibration, and we develop a qualitative model to describe the bonding and movement of hydrogen, based on a distribution of weak Si-Si bonds.

Fundamental studies and device application of δ-doping in GaAs Layers and in AlxGa1−xAs/GaAs heterostructures

Abstract: In addition to the realization of atomically abrupt interfaces in III–V semiconductors by molecular beam epitaxy, the confinement of donor and acceptor impurities to an atomic plane normal to the crystal growth direction, calledδ-doping, is important for the fabrication of artifically layered semiconductor structures. The implementation ofδ-function-like doping profiles by using Si donors and Be acceptors generates V-shaped potential wells in GaAs and AlxGa1−xAs with a quasi-two-dimensional (2D) electron (or hole) gas. In this review we define three areas of fundamental and device aspects associated withδ-doping. (i) The prototype structure ofδ-doping formed by a single atomic plane of Si donors in GaAs allows to study the 2D electron gas by magnetotransport and tunneling experiments, to study the metal-insulator transition, and to study central-cell and multivalley effects. In addition, non-alloyed ohmic contacts to GaAs and GaAs field-effect transistors (δ-FETs) with a buried 2D channel of high carrier density can be fabricated fromδ-doped material. (ii) GaAs sawtooth doping superlattices, consisting of a periodic sequence of alternating n- and p-typeδ-doping layers equally spaced by undoped regions, emit light of high intensity at wavelengths of 0.9 <λ <1.2 [μm], which is attractive for application in photonic devices. The observed carrier transport normal to the layers due to tunneling indicates the feasibility of this superlattice as effective-mass filter. (iii) The confinement of donors (or acceptors) to an atomic (001) plane in selectively doped AlxGa1−xAs/GaAs heterostructures leads to very high mobilities, to high 2D carrier densities, and to a reduction of the undesired persistent photo-conductivity. Theseδ-doped heterostructures are thus important for application in transistors with improved current driving capabilities.

New doping method for subhalf micron trench sidewalls by using an electron cyclotron resonance plasma

Abstract: A new doping method for the vertical sidewall of a trench by electron cyclotron resonance plasma is described. The plasma was produced under a pressure of 5×10−4 Torr. A doped layer was formed uniformly along the sidewall of a trench with subhalf micron width and an aspect ratio of 6.2. By using a de‐ionized water cooling system, the wafer temperature was maintained below 120 °C and the boron dopant was introduced without damage to the photoresist.

Method for etching an aluminum film doped with silicon

Abstract: A process for etch of Silicon doped Aluminum films which utilizes the combination of remote and in situ plasma in a low pressure process module and the plasma is generated from a mixture of Helium, BCl 3 , and Cl 2 , and with the process chamber within the process module being generally at ambient temperatures.

Thin film solar cell including a spatially modulated intrinsic layer

Abstract: One or more thin film solar cells in which the intrinsic layer of substantially amorphous semiconductor alloy material thereof includes at least a first band gap portion and a narrower band gap portion. The band gap of the intrinsic layer is spatially graded through a portion of the bulk thickness, said graded portion including a region removed from the intrinsic layer-dopant layer interfaces. The band gap of the intrinsic layer is always less than the band gap of the doped layers. The gradation of the intrinsic layer is effected such that the open circuit voltage and/or the fill factor of the one or plural solar cell structure is enhanced.

Electrical properties of ytterbium‐doped InP grown by metalorganic chemical vapor deposition

Abstract: A study has been carried out on the electrical properties of ytterbium‐doped InP grown by metalorganic chemical vapor deposition for the purpose of clarifying the electrical behavior of ytterbium impurities in InP. The epilayers were characterized by Hall effect measurements and by deep level transient spectroscopy. The results strongly suggest that ytterbium introduces an acceptor‐like level 0.03±0.01 eV below the conduction band which is related to isolated ytterbium atoms or single ytterbium atoms complexed with native defects. No signs of precipitation or clustering of ytterbium are observed for concentrations below 1018 cm−3 . Contrary to previous hypotheses, no evidence has been found for the existence of an ytterbium‐related acceptor level in the lower half of the band gap.

Absorption saturation in commercial and quantum-confine CdSexS 1− x-doped glasses

Abstract: The optical nonlinearity of commercial and experimental CdSexS1−x glasses has been studied using a single-beam absorption saturation technique employing 1−5-psec pulses. Glasses showing strong three-dimensional quantum-confinement effects were found to be more difficult to saturate than glasses with larger crystallites that exhibit bulk crystallike optical properties. The effect of anion stoichiometry on the nonlinearity was also studied in non-quantum-confined glasses. Within the range 0.48 < x ≤ 1.0, little difference in nonlinearity was observed.

Plasma doping process and apparatus therefor

Abstract: In a plasma doping process utilizing a radio frequency discharging in a vacuum by for doping an impurity into a semiconductor substrate, the radio frequency discharging is made intermittently and under controlling of average current of the discharging, thereby the impurity concentration is desirably controlled; and especially by selecting the vacuum in a range between 1×10 -4 -5×10 -2 torr, undesirable deposition of the impurity on the substrate surface is evadable.