Showing papers on "Doping published in 1985"

Group III Impurity Doped Zinc Oxide Thin Films Prepared by RF Magnetron Sputtering

Abstract: The detailed study of electrical properties in group III impurity doped ZnO thin films prepared by rf magnetron sputtering is described. The resistivity is lowered by doping of B, Al, Ga and In into ZnO films. The characteristic features of ZnO films doped with group III elements except for B are their high carrier concentration and low mobility. Variation of the mobility with the impurity content is roughly governed by the ionized impurity scattering. It is shown that the doped ZnO films exhibit the resistivity dependence on film thickness below 300 nm.

1.54‐μm electroluminescence of erbium‐doped silicon grown by molecular beam epitaxy

Abstract: The feasibility of producing erbium‐doped silicon light‐emitting diodes by molecular beam epitaxy is demonstrated. The p‐n junctions are formed by growing an erbium‐doped p‐type epitaxial silicon layer on an n‐type silicon substrate. When the diodes are biased in the forward direction at 77 K they show an intense sharply structured electroluminescence spectrum at 1.54 μm. This luminescence is assigned to the internal 4f–4f transition 4I13/2→4I15/2 of Er3+ (4f11).

Microstructure and formation mechanism of porous silicon

Abstract: A systematic study is presented of the effects of silicon dopant type, resistivity, current density, and hydrofluoric acid concentration on the formation and properties of porous silicon. Cross‐section transmission electron microscopy revealed the presence of two distinct microstructures. The structure formed is determined by the doping level with the transition occurring near degeneracy. A model of the anodisation process is presented which is based on the semiconducting properties of the material and which explains the formation of the two different types of porous structure observed.

Limited reaction processing: Silicon epitaxy

Abstract: We introduce a new technique, limited reaction processing, in which radiant heating is used to provide rapid, precise changes in the temperature of a substrate to control surface reactions. This process was used to fabricate thin layers of high quality epitaxial silicon. Abrupt transitions in doping concentration at the epitaxial layer/substrate interface were achieved for undoped films deposited on heavily doped substrates.

Crystal orientation dependence of silicon doping in molecular beam epitaxial AlGaAs/GaAs heterostructures

Abstract: Results on crystal orientation dependence of n‐ and p‐type Si doping in molecular beam epitaxial GaAs are presented. High electron and hole mobilities in AlGaAs/GaAs heterostructures on high index planes are demonstrated for the first time. The doping results should prove useful for various transistor structures and complementary circuits. Also, due to the differences in the band structure for different orientations, quantum well heterostructures are likely to exhibit many interesting phenomena which are strongly orientation dependent.

Ultrafast carrier and grating lifetimes in semiconductor-doped glasses

Abstract: The time dependence of both the photoluminescence due to carrier recombination and the gratings created by degenerate four‐wave mixing were measured in semiconductor‐doped color‐filter glasses. Values ranging from 80 to less than 16 ps (laser pulse width limited) are measured in several different samples at various excitation levels. A slower mechanism, believed to be thermal in nature, is also observed with a lifetime in excess of 9 ns.

Microwave and millimeter wave phase shifter

Abstract: A variable phase shifter based on the slow-wave effect for operation in the millimeter wave region, comprising a GaAs substrate for mechanical support; an n + doped semiconductor layer disposed on the GaAs substrate for operation as a first ground plane; an n doped semiconductor layer disposed on the n + semiconductor layer with a thickness to permit only one mode at millimeter wave frequencies to propagate, while suppressing higher order millimeter wave modes; and a Schottky metal microstrip with first and second ends disposed on top of the n doped semiconductor layer. Means are provided in the form of ohmic contacts for electrically connecting the n + semiconductor layer to ground electrical potential. These ohmic contacts are disposed on top of the n doped layer, but are provided with a very large surface area contact to the n doped layer in order to significantly reduce the resistance between the ohmic contact and to the n + semiconductor layer. Means are included for providing an electrical bias voltage between the Schottky metal microstrip and the n + doped layer. The propagating phase velocity of millimeter waves propagating along the Schottky metal microstrip can be varied in accordance with the bias voltage to obtain a desired phase shift between the first and second ends of the metal microstrip. In one embodiment, a metallic second ground plane is disposed on the other face of the semiconductor substrate. In a preferred embodiment, the n doped semiconductor layer is approximately 2 microns or less in thickness.

Effect of hydrostatic pressure, temperature, and doping on self-diffusion in germanium.

Abstract: The tracer-diffusion coefficient for $^{71}\mathrm{Ge}$ has been measured in Ge single crystals as a function of pressure, temperature, and doping Ion-beam sputtering was used for microsectioning The activation volume in intrinsic Ge increases slightly with temperature from 024\ensuremath{\Omega} at 876 K to 041\ensuremath{\Omega} at 1086 K (\ensuremath{\Omega} is the atomic volume) The fairly small values of the activation volume show that the defect or defects which act as diffusion vehicles must be either strongly relaxed and/or spread out Measurements of the doping dependence performed at 973 K show that the diffusivity increases with n doping and decreases with p doping This supports the view that self-diffusion in Ge proceeds by a vacancy mechanism and that the vacancy acts as an acceptor As a consequence the contribution of negatively charged vacancies, which is about 77% for intrinsic material, increases (decreases) with n doping (p doping) The measurements of the pressure dependence of the diffusivity in doped materials, also performed at 973 K, show that the activation volume is larger for pth volume for the neutral vacancy and 028\ensuremath{\Omega} for the negatively charged vacancy

Drive‐level capacitance profiling: Its application to determining gap state densities in hydrogenated amorphous silicon films

Abstract: We have developed a new method of capacitance profiling which is greatly superior to standard profiling techniques for materials like amorphous silicon that contain high densities of deep gap states. This technique, which makes use of the variation of the junction capacitance with the alternating voltage amplitude, is largely immune to the effects of surface states and is readily interpreted in terms of a simple integral over the density of states, g(E). This method is applicable to both doped and semi‐insulating undoped samples.

Electronic properties of semiconductor alloy systems

Abstract: Semiconductor alloys provide a natural means of tuning the magnitude of the forbidden gap and other material parameters so as to optimise and widen the application of semiconductor devices. With the advent of small-structure systems, such as quantum wells and superlattices, the effects of alloy composition, size, device geometry, doping and controlled lattice strain can be combined to achieve maximum tunability. The concepts and ideas peculiar to the description and modelling of semiconductor alloy systems are reviewed with a view to providing a link between electronic structure and optical and transport properties.

Molecular Semiconductors: Photoelectrical Properties and Solar Cells

Abstract: I Basic Notions of Solid State Physics.- I.1 Dark Conductivity: Generalities.- I.2 Conduction in Metals: Drude and Sommerfeld Models.- I.3 Band Model of Conduction.- I.4 Limitations to Band Theory.- I.5 Hopping and Tunneling Mechanisms of Charge Migration.- I.6 Charge Carrier Trapping Processes.- a Molecular Crystals.- b Polymers.- II Photoelectric Phenomena in Molecular Semiconductors.- II. 1 Light Absorption.- II.2 Energy Migration in Molecular Materials.- a Mechanisms of Energy Migration.- b Effect of Traps.- II.3 Photogeneration of Charge Carriers.- II.4 Semiconductor Junctions.- a p-n Junctions: Formation and Electrical Properties.- b Schottky Junctions: Semiconductor-Metal Contacts.- c Insulator-Metal Contacts.- II.5 Photovoltaic Effect.- a Molecular Solar Cells: Classical Formulation.- b Molecular Solar Cells: Localized States Formulation.- c Effect of Surface States.- d Characterization of Junctions by the Capacitance Method.- III Metallophthalocyanines.- III. 1 Syntheses and Physico-Chemical Properties.- a Syntheses.- b Structure and Morphology.- c Spectroscopic Properties.- d Photoelectron Spectroscopy.- e Oxidation-Reduction Properties.- f Electron Spin Resonance Measurements (ESR).- III.2 Dark Electrical Properties.- a Energy Band Structures.- b Electrical Properties: Intrinsic Case.- c Determination of the Trapping Levels.- d Doping of PcM by O2.- e Doping of PcM by other Doping Agents.- III.3 Photovoltaic Effect and Solar Cells.- a Photoelectrical Properties.- b Photovoltaic Effect: Generalities.- c Junction in the Dark.- d Junction Studies under Illumination.- e Effect of Doping on the Performances of Molecular Solar Cells.- f Solar Energy Conversion Efficiencies of Molecular Solar Cells.- IV Poly acetylene.- IV. 1 Synthesis and Physico-Chemical Properties of Polyacetylene.- a Synthesis.- b Morphology.- c Molecular Weight and Length of the Conjugated Sequences.- d Stability of Polyacetylene and Effect of O2.- e Isomers.- f Crystalline Structures.- IV.2 Theoretical Properties.- a Origin of the Band Gap.- b Band Structure.- c Bond Length Alternation Defects in Polyenes: the Solitons.- IV.3 Properties of Doped Polyacetylene.- a Dopants and Doping Processes.- b Structural Features.- c Optical Properties.- d Magnetic Properties.- IV.4 Transport Properties of Polyacetylene.- a Conduction Mechanisms at Low Doping Levels.- b Semiconductor-Metal Transition.- c Metallic Domain.- d Comparison of the Models with the Experimental Results in the Low Dopant Concentration Domain.- IV. 5 Photoelectric Properties and Solar Cells.- a Luminescence and Photoconductive Properties of Cis- and Trans- Poly acetylene.- b Junctions Properties and Molecular Solar Cells.- V The Main Other Molecular Semiconductors.- V. l Aromatic Hydrocarbons and Graphite.- V.2 Metallo-Organic Derivatives.- V.3 Charge Transfer Systems.- a Different Types of Charge-Transfer Systems.- b Charge Distribution.- c Charge-Transport Properties.- d Tetrathiofulvalene-tetracyanoquinodimethane (TTF-TCNQ) and Related Complexes.- e (Tetramethyltetraselenofulvalene)2-X and Related Radical-Ion Salts.- V.4 Polysulfurnitride and Polydiacetylene.- V.5 Polymethines.- V.6 Polymeric Conjugated Systems.- a Polyphenylene and Related Materials.- b Substituted Polyacetylenes, Phenylacetylene.- c Pyrolyzed Polyacrylonitrile.- d Polypyrroles.- V.7 Molecular Solar Cells.- a Squaric Acid and Merocyanine.- b Aromatic Derivatives.- c Aromatic Liquid Crystals.- d Chlorophylls and Porphyrins.- e Polymeric Systems.- Conclusion.- References.

Deep and resonance states in A IV B VI semiconductors

Abstract: This review presents the results of experimental and theoretical studies to detect and investigate deep levels associated with impurities and intrinsic defects in AIV BVI semiconductors. Group-III impurities are discussed in greatest detail. The experiments (electrophysical, optical, thermophysical) indicate the existence of localized and resonance states in materials doped with indium and thallium, and also (less unambiguously) with gallium and aluminum. Stabilization of the chemical potential is especially clearly manifested in indium doping, and it leads to an extremely high electrical homogeneity of the specimens, as revealed by the long-term relaxation of the concentration of nonequilibrium electrons. The Fermi level substantially varies with the composition of the material, the temperature, and the pressure. Upon doping with thallium, one observes a strong resonance scattering of holes, an electronic heat capacity arising from the impurity, and superconductivity caused by the presence of resonance states. The theoretical and experimental data on localized and resonance states associated with vacancies and complexes of intrinsic defects, and also with impurities of transition metals, bismuth, cadmium, tin, and germanium are reviewed. The genesis of the levels, the energy of interaction of electrons at an impurity center, relaxation mechanisms, and superconductivity are discussed.

Simultaneous measurement of hole lifetime, hole mobility and bandgap narrowing in heavily doped n-type silicon

Abstract: The hole diffusion length, hole lifetime, hole mobility, and hole equilibrium concentration in epitaxial heavily phosphorus-doped silicon have been measured by a combination of steady-state and transient techniques. Steady state measurements were performed on bipolar transistors in which the base was epitaxially grown. The transient measurement relied on the observation of the decay of the photoluminescence radiation after laser excitation. Significant findings are: 1) the hole mobility is about a factor of two larger in heavily doped n-type silicon than in p-type silicon; 2) the apparent bandgap narrowing is smaller than previously thought, with a value of about 90 meV at a doping level of 1020cm-3.

Molecular beam epitaxial growth of GaAs on Si(211)

Abstract: The molecular beam epitaxial growth of GaAs on Si(211) has been investigated. Theoretical considerations had suggested the (211) orientation to be particularly suitable for the nucleation and growth of a zincblende‐type compound semiconductor on a diamond‐type elemental one. The experimental results support the theoretical prediction. Morphologies of thin (≤0.1 μm) (211) layers are substantially better than for (100) layers, which nucleate poorly and require large layer thicknesses (≂1μm) to yield good morphologies. When the (211) layer growth is initiated with a thin (GaAs/Al, Ga)As superlattice buffer (0.1 μm), consisting of 10 periods of 5+5 nm, the (211) morphology rivals that of GaAs(100) homoepitaxial growth. Chemical etching studies as well as transmission electron microscope investigations show the layers to have the (211)B orientation and to be free of antiphase domains, both as predicted. The (211) layers show strong photoluminescence at 4 K. Not intentionally doped layers are n type, with elect...

ESR and Transport Studies in Electrochemically Doped Polythiophene Film

Abstract: Electron spin resonance (ESR), electrical conductivity and thermoelectric power are studied in electrochemically prepared and doped polythiophene films. The ESR spin density increases by two orders of magnitude up to dopant concentration of ca. 3 mol%, then decreases, while the conductivity increases drastically by more than ten orders of magnitude until this doping level, followed by a rather mild increase. The ESR linewidth decreases sharply from 9 G to 0.4 G upon slight doping with shape change from Gaussian to Lorenzian. The contribution of Pauli-paramagnetism to the spin succeptibility and the positive thermoelectric power of ca. 20 µV/K which depends linearly on the temperature are observed at heavily doped region. These results are discussed in terms of shallow and deep polarons, and formation of bipolaron up to intermediate doping levels and the hole conduction at the metallic regime.

Localized states in doped amorphous silicon

Abstract: Doping in amorphous silicon is reviewed, with particular focus on the localized states introduced by doping, and the physical origin of the effects. Many experiments find that doped a-Si:H contains a large density dangling bonds and that the doping efficiency is low and concentration dependent. Recent experiments have given much new information about shallow states near the band tails. Neutral donors are observed directly by their hyperfine structure in ESR. A doping model is described which accounts for most of the data. However, many aspects of the doping process remain to be resolved.

Method of making high breakdown voltage semiconductor device

Abstract: A multiple-zone junction termination extension region is formed adjacent a reverse-blocking junction in a semiconductor device to increase the breakdown voltage of such device. A single mask is used to form the multiple-zone JTE region, with the mask having different patterns of openings in the different zones of the mask. Adjacent openings are maintained with a center-to-center spacing of less than 25 percent of the depletion width of the reverse-blocking junction in a voltage-supporting semiconductor layer adjoining the reverse-blocking junction at the ideal breakdown voltage of the junction. As a consequence, the resulting non-uniformities in doping of the various zones of the JTE region are negligibly small. An alternative JTE region is finely-graduated in dopant level from one end of the region to the other, as opposed to having multiple zones of discrete doping levels.

Doping interface dipoles: Tunable heterojunction barrier heights and band‐edge discontinuities by molecular beam epitaxy

Abstract: We have succeeded for the first time in artificially tuning the conduction and valence‐band barrier heights at an abrupt intrinsic semiconductor‐semiconductor heterojunction via a doping interface dipole (DID). This is achieved by means of ultrathin ionized donor and acceptor sheets in situ grown within ≲100 A from the heterointerface by molecular beam epitaxy. In the limit of a few atomic layers separation between the charge sheets this amounts to modify the effective band‐edge discontinuities. A near one order of magnitude enhancement in the photocollection efficiency of an abrupt AlGaAs/GaAs heterojunction has been observed as result of the conduction‐band barrier lowering induced by the DID.

Semiconductor devices with at least one monoatomic layer of doping atoms

Abstract: A semiconductor device consisting of epitaxial material is provided with at least one monoatomic layer of doping atoms, i.e. with a layer which is just one atom thick. A particularly preferred device is a field effect transistor in which case the Dirac-delta doped layer 13 extends between the source and drain zones (18, 19) respectively. The field effect transistor can be constructed either with a homogeneous structure or with a hetero structure or with a superlattice structure. The field effect transistors described herein have a high transconductance and are capable of operating at high current densities.

Magnesium-doped lithium niobate for higher optical power applications

Abstract: Compositions of lithium niobate containing 4.5 at.% or more MgO have the ability to transmit, without distortion, light 100 times as intense as undopecl compositions. Holographic diffraction measurements of photorefraction have demonstrated that the improved performance is due to a hundredfold increase in the photoconductivity, rather than to a decrease in the Glass current. The damage-resistant compositions are also distinguished by a thermal activation energy of 0.1 eV for the diffraction efficiency, an OH-stretch vibration at 2.83 Am, a lattice phonon absorption at 21.2 Am, an electron spin resonance signal for Fe impurities at 1500 G, and, after reduction by heating in a vacuum, an optical absorption band at 1.2 um. (The corresponding values for undopedl LiNbO3 are 0.5 eV, 2.87 um, 21.8 um, 790 G, and 0.5 um, respectively.) The high photoconductivity is thus related to a distinctive electronic environment for impurities in the damage-resistant crystals. The photoconductivity strongly affects the impedance and time constants of signal processing devices made of LiNbO3.

Semiconductor memory device

Abstract: PURPOSE:To obtain an amorphous nonvolatile memory, which has excellent holding characteristics and reproducibility and a large area and large capacitance and cost thereof is low, by using an amorphous silicon carbide film in place of an amorphous silicon nitride film. CONSTITUTION:An insulating substrate 11, a lower electrode 12, an N type 13, which is hydrogenated previously by amorphous silicon and to which phosphorus is doped to a high degree, and an N type 14 to which phosphorus is doped similarly to a low degree are formed in the order. An silicon oxide film 15 in which amorphous silicon in oxidized through plasma anodizing, etc., a film 16, which consists of a hydrogenated amorphous silicon carbide film and contains carbon by 35atom% or more, and an upper electrode 17 are shaped in the order. Accordingly, a device having performance, which has not exist as nonvolatile memories, such as, a holding time of ten years or more, a writing time of 0.1musec or less, even fast erasing speed, a large area and large capacitance and low cost is obtained.

Method of forming transistors with poly-sidewall contacts utilizing deposition of polycrystalline and insulating layers combined with selective etching and oxidation of said layers

Abstract: Improved bipolar transistors having minimum base-collector and collector-substrate junction area are formed by using multiple polycrystalline (e.g. doped poly silicon) layers to make lateral contact to a pillar shaped single crystal device region. The lateral poly silicon contacts are isolated from each other and the substrate and extend to the upper surface of the device for external connections. The structure is made by depositing two dielectric-poly layer sandwiches, etching and oxidizing part of the poly silicon layers to provide isolated overlapping poly silicon regions, etching a first hole through both poly silicon regions to the substrate, etching a second hole to the lower poly silicon layer, and filling the first and second holes with single and poly-crystalline silicon, respectfully. A sidewall oxide is formed at the periphery of the top of the single crystal pillar for defining the emitter location without additional masking.

X‐ray double crystal diffraction study of porous silicon

Abstract: Depending on the dopant concentration, two distinct types of porous silicon can be formed during the anodization of silicon in hydrofluoric acid. A range of samples of both types of porous silicon has been investigated using x‐ray double crystal diffraction techniques. The crystal lattice of porous silicon is found to be tetragonally distorted. In the plane of the substrate, the interplanar spacing of the porous film is identical to that of the substrate but is increased in the direction normal to it. The increase is typically 700 ppm in the type of film formed on heavily doped silicon and 6000 ppm in that on lightly doped silicon. We propose that stresses, generated by the growth of a native oxide on the surface of the pores, are responsible for the observed increase in lattice parameter. The different interplanar spacings of the two types of film are related to the observed differences in their oxygen contents which are a consequence of their different surface area to volume ratios.

Ultra-shallow high-concentration boron profiles for CMOS processing

Abstract: The fabrication of ultra-shallow high-concentration boron profiles in silicon has been carried out utilizing a XeCl excimer laser. The Gas Immersion Laser Doping (GILD) process relies on a dopant species, in this case diborane (B 2 H 6 ), to be adsorbed on the clean silicon surface and subsequently driven in during a melt/regrowth process initiated upon exposure to the short laser pulse. Secondary Ion Mass Spectrometry and spreading resistance profiles show peak boron concentrations from 5 × 1019cm-3to 5 × 1020cm-3depending on the number of laser pulses, with junction depths from 0.08 to 0.16 µm depending on the laser energy. Electrical characteristics show essentially ideal diode behavior following a 10-s 950°C anneal.

Diffusion and electrical properties of silicon‐doped gallium arsenide

Abstract: The amphoteric nature of silicon in gallium arsenide is used to develop diffusion and electrical compensation mechanisms. The diffusion mechanism is based on the formation and diffusion of nearest‐neighbor donor‐acceptor pairs. General solutions are presented that predict abrupt diffusion fronts for a wide range of pairing conditions. Experiments support the application of this mechanism to Si diffusion in GaAs at high concentrations. A compensation mechanism for amphoteric dopants is developed as well. The compensation process is driven primarily by the free‐electron concentration. Nearly complete compensation is predicted for large dopant concentrations.

Characterization of high-purity Si-doped molecular beam epitaxial GaAs

Abstract: High‐purity, lightly Si‐doped (μ77∼70 000–126 000 cm2/V s and n77∼2–8×1014 cm−3) molecular beam epitaxy (MBE) GaAs layers have been characterized using variable‐temperature Hall effect and C‐V measurements, photothermal ionization spectroscopy, low‐temperature photoluminescence (PL), and deep level transient spectroscopy (DLTS). The spectroscopic measurements of the residual donors and acceptors indicate that the pronounced increase in carrier concentration which is observed with increasing As flux (for a constant Ga flux) results from incorporation of additional residual S donors from the As source material, and not from reductions in the Si acceptor concentration or residual C acceptor concentration. The increase in carrier concentration with As flux is considerably more pronounced when using an alternative source of As, which introduces both S and 3 additional donor species. The C acceptor concentration increases with As flux using either As source, although the increase is much stronger with the alter...

First evidence of crystalline structure in conducting polythiophene

Abstract: In order to optimize the properties of organic conducting polymers we analysed the effect of structure and dopant. The substitution of theβ carbon atoms in thiophene leads to a higher regularity in the corresponding polymer, obtained by electrochemical oxidation. The trifluoromethylsulphonate anion appears to be the best fitting dopant, allowing a 1∶2 doping level of the polymer. Transmission electron microscopy reveals crystal patterns for this highly doped polymer. The obtained electron diffraction and X-ray data are consistent with a hexagonal lattice. The discussion of these results lead us to propose a coil structure for this organic conducting polymer.

Thin film solar cell with ZnO window layer

Abstract: A thin film photovoltaic device comprising a first layer of copper indium diselenide p-type semiconductor and a second layer of n-type zinc oxide semiconductor. In a preferred form, the first portion of the zinc oxide film at the junction with the CIS is undoped to have relatively high resistivity, while the remaining portion thereof is doped to achieve low resistivity. The zinc oxide is preferably deposited by a low temperature chemical vapor deposition process.