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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown pseudomorphic InxGa1−xAs/In0.52Al0.48As modulation-doped heterostructures by molecular-beam epitaxy under carefully controlled growth conditions. Mobilities as high as 13 900, 74 000, and 134 000 cm2/V s are measured at 300, 77, and 4.2 K in a heterostructure with x=0.65. Shubnikov–de Haas measurements indicate that the change in the effective mass with increasing In is not significant and is not responsible for the enhancement in mobilities. We believe that the improvement results from reduced alloy scattering, reduced intersubband scattering, and reduced impurity scattering, all of which result from a higher conduction-band offset and increased carrier confinement in the two-dimensional electron gas. The high-field electron velocities have been measured in these samples using pulsed current-voltage and pulsed Hall measurements. A monotonic increase in velocities is observed both at 300 and 77 K with an increase of In content in the channel. Velocities of 1.55×107 and 1.87×107 cm/s are measured at 300 and 77 K, respectively, in a In0.65Ga0.35As/In0.52Al0.48As modulation-doped heterostructure.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have examined the growth and device characteristics of In0.53+x Ga0.47−x As/ In0.52 Al0.48 As (0≤x≤0.27) pseudomorphic modulation-doped field-effect transistors on InP substrates. In situ reflection high energy electron diffraction oscillation studies were carried out to study the growth of pseudomorphic InGaAs on GaAs and InP substrates. The data from these measurements and a theoretical formalism based on energy minimization suggest that in the pseudomorphic growth regime increased strain causes growth modes to change from two-dimensional layer-by-layer to a three-dimensional island mode. The resulting interface roughness is used as a parameter to explain the observed trends in channel mobility and device performance. It is also shown that altered growth techniques, such as migration enhanced epitaxy, in which the surface reconstruction may be changed, can restore the layer-by-layer growth mode for large amounts of strain in the pseudomorphic layer.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7988-7993 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the electrical and optical properties of silicon (Si)-doped InP layers grown by solid-source molecular beam epitaxy using a valved phosphorus cracker cell. Within the range of Si effusion cell temperatures investigated (900–1200 °C), the highest electron concentration obtained was 1.1×1020 cm−3. A saturation phenomenon was observed for the electron concentration at higher Si cell temperatures. 300 and 77 K Hall mobility data were used to determine the compensation ratios by comparing them with the theoretical data. Although the Hall data show that the compensation ratio increases with the increase in carrier concentration, the exact values are not certain because the theoretical calculation overestimates the mobility values at higher carrier concentrations. The saturation phenomenon of electron concentration in InP may be considered due to the Si atoms occupying both the In and P lattice sites, or Si donors located at the interstitial sites. The 300 K Hall mobility and the concentration data measured were found to fit the Hilsum expression well. The mobility values obtained in this study are better than or comparable to reported data in the past, indicating good material quality. 5 K photoluminescence (PL) measurements showed two peaks for the undoped and low doped InP layers corresponding to the neutral donor-bound exciton transitions (D0–X) and the acceptor-related transitions (D–A), respectively. When the doping level was increased, the near-band edge (D0–X) recombination peak becomes broadened and asymmetric due to changes in the donor level density of states and relaxation of the wave vector conservation rule. The full-width at half-maximum (FWHM) value of the PL peak position increased when the doping concentration was increased. An empirical equation was developed to fit this variation, which provides a convenient way of determining the dopant concentration from the experimental FWHM value. The near-band edge peak positions shifted to higher energy with the increase of doping level due to the band filling effect. This shift agreed well with the calculations based on the Burstein–Moss shift and the band gap narrowing effect considering a nonparabolic conduction band. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 869-871 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InP/InGaAs double-heterojunction bipolar transistor (HBT) structures were grown metamorphically on GaAs substrates by solid-source molecular-beam epitaxy. A linearly graded InxGa1−xP (x varying from 0.48 to 1) buffer layer was used to accommodate the strain relaxation. The crystallinity of the buffer layer and the HBT structure was examined by x-ray diffractometry. Devices with 5×5 μm2 emitter area showed a typical peak current gain of 40, a common-emitter breakdown voltage (BVCEO) higher than 9 V, a current gain cut-off frequency (fT) of 46 GHz, and a maximum oscillation frequency (fmax) of 40 GHz. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 728-730 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the properties of In0.52Al0.48As/In0.53+xGa0.47−xAs high electron mobility transistors is carried out for 0%, 7%, and 12% excess In values in the channel. Theoretical analysis shows that the enhanced In causes a biaxial compressive strain of 0.49% to 0.84% in the channel, increases the band-edge discontinuity from 0.437 to 0.500 eV, and reduces the carrier mass by 6%. Experimental characterizations support the theoretical predictions by demonstrating an increase of mobility from 9900 to 11 200 cm2/V s at 300 K, and a transconductance enhancement from 160 to at least 230 mS/mm.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Selective regrowth, which involves the growth of a device structure, patterning, etching and epitaxial regrowth of another device structure is an important technique for monolithic integration. The nature of the surface before the regrowth is crucial for realizing good quality regrown devices. In this study, the effect of different GaAs surface preparation processes on the electrical and optical characteristics of a regrown pseudomorphic high electron mobility transistor (PHEMT) is studied. Using photoluminescence, Hall, atomic force microscopy and d.c. and microwave measurements on devices, an optimized process sequence has been identified to fabricate PHEMT structures with equivalent characteristics of those grown on epiready wafers.
    Type of Medium: Electronic Resource
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