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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2063-2065 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A hole concentration greater than 1020 cm−3 in GaAs has been achieved using a liquid CCl4 source for carbon in a low-pressure organometallic vapor phase epitaxy system. The resistivity and hole mobility measured at 300 K for a heavily carbon-doped (1.2×1020 cm−3) Hall sample made from a thin (180 nm) epitaxial layer were 8.0×10−4 Ω cm and 65 cm2/V s, respectively. Carbon-doped samples with excellent surface morphology were achieved using a V/III ratio of 22, and growth pressure and temperature of 80 Torr and 600 °C, respectively. A novel photoluminescence technique, based on band-gap shrinkage of heavily doped p+-GaAs, has been shown to be useful for nondestructive measurement of the hole concentration in submicrometer layers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1552-1554 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comparison of device characteristics for In0.1 Ga0.9 As metal-semiconductor field-effect transistors (MESFETs) fabricated on GaAs and silicon substrates. The In0.1Ga0.9As layers are heteroepitaxially grown on GaAs and silicon substrates by metalorganic chemical vapor deposition. 0.5 μm gate devices fabricated on the GaAs substrate show a maximum extrinsic transconductance of 450 mS/mm and a current-gain cutoff frequency ft of 55 GHz. Despite the large lattice mismatch, the In0.1 Ga0.9 As MESFETs fabricated on the silicon substrate show a comparable ft of 52 GHz with a lower gain.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1233-1235 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental evidence that current gain cutoff frequency (ft) values equal to or greater than those achieved with high electron mobility transistors (HEMTs) and pseudomorphic HEMTs can also be achieved by ion-implanted GaAs and InGaAs metal-semiconductor field-effect transistors. These measured ft results clearly suggest that the average electron velocity under the gate is determined primarily by the high-field electron velocity rather than the low-field electron mobility. Hence, we conclude that the transport properties of the two-dimensional electron gas in HEMTs and pseudomorphic HEMTs do not make a significant contribution to the high-frequency and high-speed performance of these devices.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extensive data are presented on impurity-induced layer disordering (IILD) of AlxGa1−xAs-GaAs quantum-well heterostructures and superlattices that are Si implanted and annealed (Si+-IILD) at three different implant doses. We show that impurity activation is not critical to the layer disordering process and that Si diffusion from the implanted profile initiates Si+-IILD. When the implant dose is as high as φ≥5×1013/cm2 (nSi ≥2×1018/cm3), Si interstitial loops (Si-ILs) form by diffusion and agglomeration of the implanted Si atoms during the initial stages of annealing. If a source of Ga vacancies is provided (e.g., via an As overpressure or SiO2 encapsulation), the Si-ILs dissociate and supply Si atoms for diffusion and hence Si+-IILD during the latter stages of annealing. If a Si3N4 encapsulant is employed, however, fewer Si-ILs form and Si diffusion is inhibited. For an implantation dose as low as φ=1×1012/cm2 (nSi =3×1016/cm3), extensive Si+-IILD is realized via capless annealing and Si-ILs are not observed. It is significant for device applications that the layer-disordered material operates as a cw 77 K photopumped laser, which indicates that the layer averaging (IILD) does not damage the crystal.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    GeoJournal 35 (1995), S. 71-77 
    ISSN: 1572-9893
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract The 25th cruise of R/F“Akademik Knipovitch” conducted in January–April of 1990 comprised investigations of total organic carbon (TOC) at the following sections: through the Polar Frontal Zone (PFZ) along 40° W, made in January and April; from the PFZ to the South Orkney Islands, and on the South Georgia shelf. The measurements made comprised TOC, organic nitrogen, nitrate, nitrite, ammonium nitrogen, phosphate and silicate. The surface waters of the region were characterized by high heat content, which influenced the Antarctic phytosynosis function. The data obtained showed low content of organic matter (OM); high content of TOC, rising up to 3,5 mg m−3, was recorded at the photic layer and in the layer of OM accumulation, at the upper boundary of the Antarctic Deep Waters and the vertical boundaries of the Antarctic Intermediate Waters. The South Georgia shelf waters showed even distribution of TOC, about 0,2 mg m−3, being under the influence of the south periphery of the ACC waters.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 1511-1518 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Investigations were carried out on polycaproamide films(PCA) at room temperature in air. Samples were dyed with oxyethylsulfonic and monochlortriasinic active dyes. Irradiation was carried out with a low-pressure Hg lamp (λ = 254 nm, intensity equals 1.5 × 1015 sm-2 sec-1). During irradiation, ESR spectra of five poorly resolved lines of superfine structure were observed for all samples. Analysis of ESR spectra shows that quintet belongs to radicals $ \sim {\rm CONH\dot CHCH}_{\rm 2} \sim $. The initial accumulation rate of radicals was measured on linear parts of radical accumulation curves. Similarly, accumulation of PCA carboxyl groups kinetics was measured. The initial accumulation rates of radicals and carboxyl groups are linear functions of absorbed radiation on polymer and dye. There is a tendency of increasing carboxyl group yields with radical yields for different dyes. One can assume that it follows from this correlation that radicals are precursors of carboxyl groups. Luminescence spectra measured for PCA with salt and covalent bonded dyes are located near 425 nm. The data allow the conjecture that PCA luminescence is connected with centers bonded with PCA macromolecules.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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