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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3912-3917 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated the patterned heteroepitaxial processing (PHP) approach for the removal of threading dislocations (TDs) from ZnSe and ZnS0.02Se0.98 on GaAs (001). PHP involves the growth of a continuous heteroepitaxial layer followed by postgrowth patterning and annealing. We found that the basic mechanism of TD removal by PHP is thermally activated dislocation motion in the presence of sidewalls. By studying the temperature dependence we showed that the activation energy for the annealing process (∼0.7 eV in ZnSe on GaAs) is consistent with dislocation motion by glide. We showed that there is a minimum mesa thickness required for the complete removal of TDs by PHP (∼3000 Å for 70 μm×70 μm mesas of ZnSe on GaAs). This is because the lateral forces acting on TDs are proportional to the mesa thickness. We also conducted a preliminary study of the mismatch dependence of PHP. Our results suggest that PHP removes TDs more effectively in the higher lattice mismatch system ZnSe/GaAs (001) than in the lower lattice mismatch system ZnS0.02Se0.98/GaAs (001). This is expected based on the mismatch dependence of the line tension forces in the misfit segments of dislocations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A time-dependent finite-difference beam propagation method is presented to analyze quantum interference transistor (QUIT) structures, employing the Aharonov–Bohm effect, in both steady state and transient conditions. Current–voltage characteristics of two ring structures having 0.2 and 0.05 μm channel lengths, respectively, are presented. Additionally, the wave functions are calculated, and reflections are observed in both the ON and OFF states of the device. Cutoff frequency fT values of 3 and 8.5 THz, respectively, are calculated from the switching response to a gate pulse of 200 fs, for the 0.2 μm device, and to a pulse of 50 fs, for the 0.05 μm device. Results indicate that reflections at the drain may degrade frequency performance of these devices, which is not evident from earlier analytical studies. These structures are further explored to investigate the effects of imperfections introduced in fabricating the quantum wire channels. We compare two QUITs, one realized by a 1 nm resolution lithography process (representing an advanced fabrication technique) and the other realized by a 10 nm resolution (representing current state-of-the-art lithography). We also present an asymmetric 10 nm resolution structure, to represent the case when errors in fabrication significantly alter the QUIT topology. This simulation shows strong dependence of the electron transmission probability on the channel topology and roughness determined by the lithographic resolution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recently, a general technique for the measurement for the threading dislocation densities in epitaxic semiconductors by high-resolution X-ray diffraction was reported [Ayers (1994). J. Cryst. Growth, 135, 71–77]. Here, this method has been extended to the case of a Barrels five-crystal diffactometer by making use of known instrumental effects for this diffractometer. The usefulness of the method has been demonstrated by application of the technique to epitaxic ZnSe grown on GaAs (001) by photo-assisted metalorganic vapor-phase epitaxy. It is shown that in this case the threading dislocation density of the epitaxic layer can be determined quantitatively. Evidence for the introduction of dislocations in the underlying GaAs substrate is also presented.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Monolithic semiconductor antennas integrated with a diode detector have been fabricated using silicon-on-sapphire technology. The performance of these antennas is analyzed on the basis of earlier theoretical work on imperfectly conducting/resistive cylindrical dipoles. The measured radiation patterns of semiconductor antennas are compared with those of the corresponding printed metal dipoles.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9559
    Keywords: Quantum Interference Transistor (QUIT) ; quantum interference ; MODFET ; unity current-gain cut-off frequency (f T) ; Aharonov-Bohm Effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A high performance quantum interference transistor (QUIT) realized using high mobility 1-D MODFET channels is presented. The operation of this 1-D QUIT is based on electrostatic Aharonov-Bohm quantum interference effect. The channel length of the device is smaller than the inelastic coherence length of the electrons in the quantum well wire channel, otherwise scattering will randomize electron's phase and destroy the quantum interference effect. Transport characteristics of the 0.2 μm channel 1-D QUIT are calculated at 4.2 °K and compared with a two-dimensional QUIT device reported in literature. Our calculations show a significant improvement of the transconductance in one-dimensional transistors compared with its two-dimensional counterpart. The maximum frequency of operation of the 1-D QUIT is in the Tera Hertz regime, which makes it very attractive device for high frequency applications.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-9559
    Keywords: Submillimeter MODFET ; Quantum Wire MODFET ; InGaAs MODFET ; CoupledWell MODFET
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A coupled-well InAlAs/InGaAs quantum wire MODFET structure is proposed, for which simulations predict improved frequency performance (〉500 GHz), over a wider range of Vg, as compared to well/wire devices with a standard MODFET heterointerface. A comparison of several transverse potential well profiles, obtained by varying the placement of a thin barrier within a 100 Å finite well, is presented. In all cases, the quantum wires consist of a 0.1 μm long channel and a 150 Å finite-square-well lateral profile. It has been found that the peak of the electron distribution for the first confined state, as measured from the heterointerface, changes dramatically depending on the location of the thin barrier. For quantum wire structures, realized in the lattice matched system of In0.52Al0.48As/In0.53Ga0.47As/InP, a change in the barrier location of 25 Å is accompanied by a shift in the carrier peak of more than 40 Å (~20 Å closer to or farther from the spacer-well interface than in the standard MODFET profile). Implications of this are reflected in the current-voltage characteristics (Id-Vd) and frequency responses (fT-Vg) of the proposed structures.
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  • 7
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A novel metal-SiO2-InP MISFET (metal-insulator-semiconductor field effect transistor) structure is proposed. This device incorporates a modulation doped channel and the self-aligned gate feature of Si MOSFETs. The modulation doping provides very high electron mobility and the self-alignment of gate, source and drain provides high packing density. Analytical results on current-voltage and transconductance characteristics are presented. Significant enhancement in high frequency performance over conventional MISFETs, employing SiO2 as an insulator, is reported.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-9559
    Keywords: MODFET ; two-dimensional electron gas (2 DEG, HFET, unity-current gain cutoff frequency f T)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A Modulation-Doped Field-Effect Transistor (MODFET) structure realized in InGaN-GaN material system is presented for the first time. An analytical model predicting the transport characteristics of the proposed MODFET structure is given in detail. Electron energy levels inside and outside the quantum well channel of the MODFET are evaluated. The two-dimensional electron gas (2DEG) density in the channel is calculated by self-consistently solving Schrödinger and Poisson's equations simultaneously. Analytical results of the current-voltage and transconductance characteristics are presented. The unity-current gain cutoff frequency (f T) of the proposed device is computed as a function of the gate voltage V G . The results are compared well with experimental f T value of a GaN/AlGaN HFET device. By scaling the gate length down to 0.25 μm the proposed InGaN-GaN MODFET can be operated up to about 80GHz. It is shown in this paper that InGaN-GaN system has small degradation in f T as the operating temperature is increased from 300°K to 400°K.
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  • 9
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transverse modal behavior of Metal-Insulator (Oxide)-Semiconductor (MIS) heterostructure injection lasers is analyzed. MIS structures have been proposed by Jain and Marciniec as an alternate approach to p-n heterojunctions to obtain minority carrier injection and subsequent lasing action. In the modal analysis the MIS structure is treated as an asymmetrical three-layer slab waveguide with appropriate boundary conditions. Numerical computations of electric field strength, intensity and confinement factor P are presented for various GaAs and InP based MIS structures. A comparison of the output characteristics of a GaAs MIS laser with a conventional GaAs p-n double heterostructure laser is also reported.
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  • 10
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It has been reported that the radiation characteristics of semiconductor antennas can be controlled by modulating their conductivity during fabrication and/or operation. This paper describes novel physical layouts integrating these versatile antennas with other components used in the realization of millimeter wave systems. The monolithic integration is discussed for GaAs as well as Si IC technologies.
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