Showing papers on "Doping published in 1986"

Evaporated Sn‐doped In2O3 films: Basic optical properties and applications to energy‐efficient windows

Abstract: We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...

Macromolecular electronic device: Field-effect transistor with a polythiophene thin film

Abstract: The first solid‐state field‐effect transistor has been fabricated utilizing a film of an organic macromolecule, polythiophene, as a semiconductor. The device characteristics have been optimized by controlling the doping levels of the polymer. The device is a normally off type and the source (drain) current can be modulated by a factor of 102–103 by varying the gate voltage. The carrier mobility and the transconductance have also been determined to be ∼10−5 cm2/V s and 3 nS, respectively, by means of electrical measurements.

Aluminum or phosphorus co-doping effects on the fluorescence and structural properties of neodymium-doped silica glass

Abstract: To utilize the excellent properties of silica (SiO2) glass for a glass laser host, neodymium‐aluminum (Nd–Al) and neodymium‐phosphorous (Nd–P) co‐doped SiO2 glasses were studied. They were prepared by plasma‐torch chemical vapor deposition (CVD). It was found that a doping level less than ten times the number of Nd for the Al co‐dopant and less than about fifteen times for the P co‐dopant was enough to remove undesirable fluorescence properties of Nd‐doped SiO2 glasses and make them suitable for laser application. The clustering Nd ions disperse well in a glass matrix and lasing fluorescence increases. The effects of the Al dopant on the density and Raman spectra were also studied to obtain structural information. On the basis of glass science and solution chemistry, the marked effects of both dopants were explained by the following model. Nd ions can be well incorporated into a SiO2 glass network through co‐dopant oxide forming a solvation shell around the Nd ions. This model leads to an expansible metho...

Grain‐Boundary Effect in Ceria Doped with Trivalent Cations: I, Electrical Measurements

Abstract: The “grain-boundary effect,” which leads to a greatly reduced dc ionic conductivity due to the presence of a blocking layer in the vicinity of the grain boundaries, is studied in detail for ceria ceramics doped with various trivalent dopants (particularly Y3+, Gd3+, and La3+). The effects of porosity, of sintering time, and of dopant size and dopant concentration are investigated. Finally, it is shown that the grain-boundary effect virtually disappears when nearly silicon-free starting materials are used.

Hydrogen passivation of shallow-acceptor impurities in p-type GaAs.

Abstract: It is shown for the first time that hydrogen passivation of p-type GaAs produces electrical compensation of the shallow-acceptor impurity. This is demonstrated with capacitance-voltage and secondary-ion-mass spectrometry measurements on hydrogenated Zn-doped GaAs. In addition, it is shown that for comparable net dopant concentrations, passivation is far more extensive in p-type as compared to n-type GaAs; both metal-organic chemical-vapor-deposited (Zn and Se doped) and bulk GaAs (Zn and Si doped) were investigated. It is proposed that hydrogen passivation of Zn acceptors in GaAs involves interstitial diffusion of hydrogen to the vicinity of a zinc atom that is located at a gallium site. The hydrogen atom specifically bonds to an arsenic atom that is adjacent to the zinc. From the experimental results it is inferred that hydrogen passivation of shallow-acceptor impurities is a general physical phenomenon in semiconductors.

Transport phenomena in amorphous silicon doped by ion implantation of 3d metals

Abstract: Charge transport in amorphous silicon (aSi) doped with ion implantation of Mn+, Ni+, Fe+, and Cu+ ions is studied using ESR technique, temperature dependence of conductivity σ(T), and thermopower α(T) measurements With increasing of impurity (Mn, Ni, Fe) concentration (from 1018to 1019 cm−3) the localized state density and σ decrease owing to the passivation of silicon dangling bonds with impurity atoms An analysis of conductivity and thermopower data allows to reveal three temperature regions 1) At 250 500 K electron transport dominates 3) At T < 250 K hopping conductivity with variable range hopping near Fermi level prevails For a-Si:Mn in the region of 4 < T < 80 K Coulomb correlations are detected in the behaviour of σ(T) The Coulomb gap is foundto reach a maximum value 25 meV which appears to be one order of value larger than the known (one) in semiconductors doped with shallow impurity levels [Russian Text Ignored]

Doping reaction of PH3 and B2H6 with Si(100)

Abstract: The reaction of phosphine PH3 and diborane B2H6 on Si(100) surfaces was studied by surface analytical techniques in relation to the in situ doping process in the chemical vapor deposition of silicon. Phosphine chemisorbs readily either nondissociatively at room temperature or dissociatively with the formation of silicon–hydrogen bonds at higher temperatures. Hydrogen can be desorbed at temperatures above 400 °C to generate a phosphorus layer. Phosphorus is not effective in shifting the Fermi level until the coverage reaches 2×1014/cm2. A maximum shift of 0.45 eV toward the conduction band was observed. In contrast, diborane has a very small sticking coefficient and the way to deposit boron is to decompose diborane directly on the silicon surface at temperatures above 600 °C. Boron at coverages less than 2×1014/cm2 is very effective in shifting the Fermi level toward the valence band and a maximum change of 0.4 eV was observed.

Properties of Pure and Doped Bi12GeO2oand Bi12SiO20 Crystals

Abstract: Bi12GeO20 (BGO) and Bi12SiO20 (BSO) single crystals doped with Al, Ga, P, Pb, Or, Nd, Zn, Fe, and Eu are grown from the melt in good optical quality. The segregation coefficients of the dopants range from 0.1 to 5. The undoped crystals are yellow; Al, Ga, and P bleach the crystals and increase their dark conductivity. The bleaching of these Bi12MO20 crystals can be explained by assuming a transformation of the absorption center (Bi + h) to B3+M with dopant P, and to B3+M with dopants Ga or Al. The photoconductive behavior, thermally stimulated currents, photolumines-cence at T = 1.3K, thermal expansion, heat capacity, and breaking strength of these crystals are also determined.

Thermal equilibration in doped amorphous silicon.

Abstract: The structure of doped amorphous silicon is shown to be in metastable thermal equilibrium above 130\ifmmode^\circ\else\textdegree\fi{}C, having temperature-dependent densities of dangling bonds and donors. The time to reach equilibrium is thermally activated, so that cooling establishes a slowly relaxing nonequilibrium state resembling a glass. The results are interpreted in terms of the recent defect-compensation model of doping.

Measurement of electron lifetime, electron mobility and band-gap narrowing in heavily doped p-type silicon

Abstract: The parameters that control the transport of minority carriers in heavily doped Si:B have been measured by a combination of steady state electrical and transient optical techniques. Electron diffusion length and electron lifetime measurements have been conducted on doped-as-grown wafers to extract the minority carrier electron mobility as a function of acceptor doping density. Effective band-gap narrowing in p+epitaxial layers has been characterized using bipolar test structures. Significant findings: 1) the electron mobility is about 2.5 times larger in heavily doped p-type Si than in n-type. 2) bandgap narrowing exceeds 120 meV at N _{A} = 2 \times 10^{20} cm-3.3) minority electron lifetime in processed p+Si is not well modeled over a large doping range by an "Auger" coefficient.

Energy relaxation of two‐dimensional electrons and the deformation potential constant in selectively doped AlGaAs/GaAs heterojunctions

Abstract: We investigate the electron heating process in selectively doped AlGaAs/GaAs heterojunctions from magnetotransport measurements at low temperatures. It is shown that the dominant energy‐relaxation mechanism of the degenerate two‐dimensional (2D) electrons for the electron temperature below 40 K is the emission of acoustic phonons via deformation potential coupling, and that the energy‐loss rate is almost independent of 2D electron densities. From a detailed analysis it is derived that the deformation potential constant of the quantized 2D conduction band in GaAs is 11±1 eV.

Thin film FET doped with diffusion inhibitor

Abstract: The present invention relates to a semiconductor device including a MOS transistor which is formed with a source region, a drain region and a channel region by the use of polycrystalline silicon, and a method of manufacturing the semiconductor device. Ions of carbon, oxygen or/and nitrogen are introduced into a polycrystalline silicon layer over the whole area thereof, and restrain conductive ions in the source and drain regions from diffusing into the channel region.

Preparation process of compound semiconductor

Abstract: A compound semiconductor thin film is formed by growing a plurality of molecular layers one over another. According to the present invention, while a carrier gas and a small quantity of hydride containing an element in Group V or VI are normally flowed, an organometallic compound which is diluted with hydrogen and which contains an element in Group III or II and a hydride which is diluted with hydrogen and which contains an element in Group V or VI are alternately introduced over a substrate so that an atomic layer of an element in Group III or II and an atomic layer of an element in Group V or VI are alternately grown over the substrate. According to this method, grown layers having a high degree of purity can be obtained. A portion such as a Ga-Ga two-layer structure formed in the growth of a surface of an element in Group III or II can easily be eliminated by the introduction of a hydrogen halide so that the surface defects and deep levels are significantly decreased and perfect crystals can be obtained. According to the present invention, a high-concentration doping of a III-V compound semiconductor becomes possible. The method of the present invention is advantageous in the fabrication of high-speed FETs and multi-quantum-well lasers using compound semiconductors.

Electronic transport in doped amorphous silicon.

Abstract: The temperature dependence of the dc dark conductivity of doped hydrogenated amorphous silicon is explained by the defect-compensation model of doping with the proposal that the structure is in metastable thermal equilibrium. Observed conductivity activation energies and preexponential factors can be accounted for quantitatively. When the localized state distribution is in thermal equilibrium, the conductivity preexponential factor is the Mott minimum metallic conductivity.

Molecular material based junctions: formation of a Schottky contact with metallophthalocyanine thin films doped by the cosublimation method

Abstract: A new method for obtaining thin films of doped molecular materials in a complete absence of oxygen is described. It consists in simultaneously subliming under vacuum the electroactive compound—a metallophthalocyanine—and the electron acceptor or electron donor doping agent. The extent of doping is controlled by the relative rates of sublimation. The ac and dc electrical properties of thin films are determined under high vacuum as to eliminate the influence of oxygen which has been previously shown to be of the utmost importance. Both p‐ and n‐type dopings have been achieved; the increase of conductivity reaches six orders of magnitude for p‐type doping with dichlorodicyanoquinone (DDQ). For the first time a rectifying contact between doped phthalocyanine thin films and aluminum has been observed in strict absence of oxygen.

Measurement of hole mobility in heavily doped n-type silicon

Abstract: Accurate measurements of the mobility (and diffusion coefficient) of minority-carrier holes in Si:P with doping in the 1019cm-3range have been done. The technique employed the measurement of diffusion length by means of lateral bipolar transistors of varied base widths, and the measurement of minority-carrier lifetime on the same wafers from the time decay of luminescence radiation after excitation with a short laser pulse. Minority-carrier hole mobility is found to be about a factor of two higher than the mobility of holes as majority carriers in p-type Si of identical doping levels.

Intentional p type doping by carbon in metalorganic MBE of GaAs

Abstract: We report on the intentional ρ-type doping of GaAs layers grown in an UHV system from molecular beams of arsine (AsH3) and mixtures of frimethyl gallium (TMG) and friethyl gallium (TEG). The entire doping range between 1014 cm-3 (growth from pure TEG) and 1020 cm-3 (growth from pure TMG) can be covered by using mixtures of TMG and TEG. As revealed by SIMS and photoluminescence (PL) carbon is the dominant acceptor in the layers. Comparison of the Hall mobility and of the PL spectra shows that the quality of our films equals that of the best LPE and MBE grown ρ-type GaAs layers.

Effect of organic contaminants on the oxidation kinetics of silicon at room temperature

Abstract: The oxidation kinetics of HF‐etched n‐ and p‐doped silicon in air at room temperature have been studied by electron spectroscopy for chemical analysis. No great differences have been found between the n‐ and p‐type oxidation kinetics at the low doping level of the studied samples. The rate of oxide growth on the HF‐etched surface is much lower than that on a silicon surface obtained by fracture in air of a silicon monocrystal. The behavior of a silicon sample fractured in de‐ionized water and then oxidized in air at room temperature is intermediate. The above findings have been interpreted on the basis of surface reactions involving the plasticizers of the HF and water containers. These reactions produce carbon‐rich hydrophobic surfaces which retard the silicon oxide growth. A mechanism for the involved surface reactions is proposed.

Multilayer semi-insulating film for hermetic wafer passivation and method for making same

Abstract: A film for hermetically passivating monocrystalline silicon includes sequential layers of undoped amorphous silicon, oxygen doped polycrystalline silicon, silicon rich oxynitride, and silicon nitride, and may be overlaid with an organic bulk dielectric such as polyimide The inorganic film accurately sets the monocrystalline surface Fermi potential, independent of ambient electrical, mechanical, thermal, ionic, and moisture conditions A method for depositing the amorphous silicon and the oxygen doped polycrystalline silicon layers of the film includes sequentially reacting monosilane in an inert carrier gas, such as helium or argon, and nitrous oxide The layers are blended by varying the deposition temperature, the nitrous oxide flow rate, the monosilane flow rate, the monosilane dilution, and the inert carrier gas species The layers are annealed to locally segregate the oxygen, to grow the grains to the proper size, and to set the final recombination velocity of the monocrystalline region

A chemical-bond approach to doping, compensation and photo-induced degradation in amorphous silicon

Abstract: We propose that during deposition of a-Si:H films a chemical equilibrium is established that relates the density of dangling-bond defects near mid-gap to the densities of electrons and holes in the conduction and valence band states. We develop the appropriate chemical reaction formalism and show that our model allows doping, compensation and photo-induced degradation to be treated within a single and unifying approach.

Phosphorus Acceptor Levels in ZnSe Grown by Molecular Beam Epitaxy

Abstract: A new doping technique for phosphorous using a Zn3P2 source has been developed. From an extensive study of the electrical properties of ZnSe doped with P, it has been found that the doped P induces point defects in excess of the doped P atoms which lowers the electron concentration and the electron mobility much more than expected. From an investigation of the low-temperature PL spectra, it was found that P forms a shallow acceptor with an activation energy of 80-92 meV in MBE-grown lightly P-doped ZnSe, and at the same time a deep acceptor with an activation energy of 0.6-0.7 eV in heavily P-doped ZnSe.

Observation of enhanced single longitudinal mode operation in 1.5‐μm GaInAsP erbium‐doped semiconductor injection lasers

Abstract: We propose a new type of current injection semiconductor laser with rare‐earth dopant in the active layer for achieving stable, single longitudinal mode operation. In this laser, the rare‐earth/semiconductor combination is chosen such that the wavelengths of the dominant emission from the trivalent rare‐earth ion internal 4f‐4f transitions are shorter than that of the band‐edge emission of the host semiconductor. Spectrally, the narrow optical gain due to the rare‐earth ion transition will superimpose on top of the broad gain peak of the host semiconductor. Such laser diodes will attain lasing action at the rare‐earth transition wavelength resulting in single longitudinal mode operation with conventional Fabry–Perot cavity. Furthermore, reproducible precise lasing wavelength insensitive to temperature variation should be possible. Such a proposed rare‐earth/semiconductor injection laser was investigated with erbium doping in the GaInAsP (λ=1.55 μm) active layer of the heteroepitaxial ridge‐overgrown lase...

Non-solitonic conductivity in polyacetylene

Abstract: Systematic investigations of the temperature dependences of the d.c. and microwave conductivity of polyacetylene doped with various species are reported. These results are discussed within a model where the measured quantities are a superposition of different conduction mechanisms. At low dopant concentrations carrier hopping between localized defect states dominates, while at high doping levels only the inter-fibrillar contact resistances are important. In an intermediate doping region the prevailing contribution to the conductivity is carrier tunnelling between highly conducting parts of the sample separated by less-conducting zones. There seems to be no doping regime in which carrier transport via mobile conjugational defects (solitons) plays a detectable role.

Modulation doped field effect transistor with doped Six Ge1-x -intrinsic Si layering

Abstract: A modulation doped field effect transistor (MODFET) having an n-conductive channel. This channel is produced by a heterostructure formed on a silicon substrate and composed of a modulation doped Si1-x Gex layer as well as an undoped Si layer.

Dopant Distribution in Nominally Yttrium-Doped Sapphire

Abstract: The dopant distribution in nominally yttrium-doped sapphire is characterized. The results indicate that virtually all of the intended dopant segregated to the surface of the crystal during growth. This implies that the solubility of yttrium in alumina is <10 ppm even at temperatures approaching the melting point of alumina.