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  • 1
    Electronic Resource
    Electronic Resource
    Two-dimensional profiling of shallow junctions in Si metal-oxide-semiconductor structures using scanning tunneling spectroscopy and transmission electron microscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2115-2121 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used cross-sectional scanning tunneling spectroscopy and cross-sectional transmission electron microscopy to perform two-dimensional profiling of shallow pn junctions in Si metal-oxide-semiconductor structures. In the tunneling spectroscopy measurements, clear differences were observed between current-voltage spectra obtained from p-type, n-type, and depleted regions of the metal-oxide-semiconductor structures; current images generated from the tunneling spectra revealed the profiles of the pn junctions with spatial resolution in both the lateral and vertical directions on the order of 10 nm. Calculated tunneling current-voltage spectra were found to be consistent with observed differences in experimental spectra obtained from p-type and n-type regions of the junctions. Junction profiles obtained by scanning tunneling spectroscopy have also been compared to transmission electron microscopy images of chemically delineated junctions and measurements of vertical dopant profiles obtained by secondary ion mass spectrometry. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361069
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of AlxGa1−xAs/GaAs heterojunction bipolar transistor structures using cross-sectional scanning force microscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1937-1942 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have characterized base-layer width and dopant distributions on cleaved cross-sections of AlxGa1−xAs/GaAs heterojunction bipolar transistor (HBT) structures using a variation of electrostatic force microscopy. The contrast observed is sensitive to the local dopant concentration through variations in the depletion layer depth extending into the sample surface, and enables delineation of individual device regions within the epitaxial layer structure with nanoscale spatial resolution. In two epitaxially grown HBT structures, one with 50 nm base width and the other with 120 nm base width, we are able to delineate clearly the emitter, base, collector, and subcollector regions, and to distinguish regions within the collector differing in dopant concentration by a factor of two. We have also distinguished clearly between the base widths in these samples and have precisely measured the difference to be 63±3 nm, in excellent agreement with the nominal difference of 70±7 nm. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372116
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  • 3
    Electronic Resource
    Electronic Resource
    Trap characterization by gate-drain conductance and capacitance dispersion studies of an AlGaN/GaN heterostructure field-effect transistor (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8070-8073 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gate-drain capacitance and conductance measurements were performed on an Al0.15Ga0.85N/GaN heterostructure field-effect transistor to study the effects of trap states on frequency-dependent device characteristics. By varying the measurement frequency in addition to the bias applied to the gate, the density and time constants of the trap states have been determined as functions of gate bias. Detailed analysis of the frequency-dependent capacitance and conductance data was performed assuming models in which traps are present at the heterojunction (interface traps), in the AlGaN barrier layer (bulk traps), and at the gate contact (metal–semiconductor traps). Bias-dependent measurements were performed at voltages in the vicinity of the transistor threshold voltage, yielding time constants on the order of 1 μs and trap densities of approximately 1012 cm−2 eV−1. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373499
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of surface processing and passivation on carrier concentrations and transport properties in AlGaN/GaN heterostructures (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1357-1361 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of surface chemical treatments and of deposition of a SiO2 surface passivation layer on carrier distributions and mobility in AlxGa1−xN/GaN heterostructure field-effect-transistor epitaxial layer structures is investigated. Surface chemical treatments are found to exert little influence on carrier distribution and mobility. Deposition of a SiO2 surface passivation layer is found to induce an increase in electron concentration in the transistor channel and a decrease in mobility. These changes are largely reversed upon removal of the SiO2 layer by wet etching. These observations are quantitatively consistent with a shift in Fermi level at the AlxGa1−xN surface of approximately 1 eV upon deposition of SiO2, indicating that the AlxGa1−xN/SiO2 interface has a different, and possibly much lower, density of electronic states compared to the AlxGa1−xN free surface. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383014
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  • 5
    Electronic Resource
    Electronic Resource
    Gate leakage current mechanisms in AlGaN/GaN heterostructure field-effect transistors (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5951-5958 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gate leakage currents in AlGaN/GaN heterostructure field-effect transistor (HFET) structures with conventional and polarization-enhanced barriers have been studied. Comparisons of extensive gate leakage current measurements with two-dimensional simulations show that vertical tunneling is the dominant mechanism for gate leakage current in the standard-barrier HFET and that the enhanced-barrier structure suppresses this mechanism in order to achieve a reduced leakage current. An analytical model of vertical tunneling in a reverse-biased HFET gate-drain diode is developed to evaluate the plausibility of this conclusion. The model can be fit to the measured data, but suggests that additional leakage mechanisms such as lateral tunneling from the edge of the gate to the drain or defect-assisted tunneling also contribute to the total leakage current. The vertical tunneling current mechanism is shown to be more significant to the gate leakage current in III–V nitride HFETs than in HFETs fabricated in other III–V material systems, in which the lateral tunneling current component generally dominates the gate leakage current. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319972
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  • 6
    Electronic Resource
    Electronic Resource
    n-CdSe/p-ZnTe based wide band-gap light emitters: Numerical simulation and design (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4660-4668 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The only II-VI/II-VI wide band-gap heterojunction to provide both good lattice match and p- and n-type dopability is CdSe/ZnTe. We have carried out numerical simulations of several light emitter designs incorporating CdSe, ZnTe, and Mg alloys. In the simulations, Poisson's equation is solved in conjunction with the hole and electron current and continuity equations. Radiative and nonradiative recombination in bulk material and at interfaces are included in the model. Simulation results show that an n-CdSe/p-ZnTe heterostructure is unfavorable for efficient wide band-gap light emission due to recombination in the CdSe and at the CdSe/ZnTe interface. An n-CdSe/MgxCd1−xSe/p-ZnTe heterostructure significantly reduces interfacial recombination and facilitates electron injection into the p-ZnTe layer. The addition of a MgyZn1−yTe electron confining layer further improves the efficiency of light emission. Finally, an n-CdSe/MgxCd1−xSe/MgyZn1−yTe/p-ZnTe design allows tunability of the wavelength of light emission from green into the blue wavelength regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352761
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  • 7
    Electronic Resource
    Electronic Resource
    Two-band modeling of narrow band gap and interband tunneling devices (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1372-1375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-band transfer matrix method has been developed to study tunneling currents in narrow gap and interband tunnel structures. This relatively simple model gives good agreement with recently reported experimental results for InAs/AlSb/InAs/AlSb/InAs double-barrier heterostructures and InAs/AlSb/GaSb/AlSb/InAs resonant interband tunneling devices, and should be useful in the design of new interband tunneling devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346688
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  • 8
    Electronic Resource
    Electronic Resource
    Role of heavy-hole states in interband tunnel structures (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 292-294 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the first calculation of transport in InAs/GaSb/AlSb-based interband tunnel structures which uses a realistic band structure model. The results are compared with calculations using a two-band model which includes only the lowest conduction band and the light-hole band. It is found that heavy-hole states can introduce substantial hole-mixing effects in device structures containing GaSb quantum wells, and should have a significant influence on current-voltage characteristics interband devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104665
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  • 9
    Electronic Resource
    Electronic Resource
    Negative differential resistance due to resonant interband tunneling of holes (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3744-3746 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current-voltage (I-V) behavior of a GaSb(p)/AlSb/InAs/AlSb/GaSb(p) resonant interband tunneling (RIT) heterostructure is analyzed experimentally and theoretically. The structure has been successfully grown on a (100)-oriented GaAs substrate by molecular-beam epitaxy, demonstrating that more exotic lattice-matched substrates (such as InAs or GaSb) are not required for RIT devices. Theoretical simulations of I-V behavior are developed, employing a two-band tight-binding model. Experimental I-V curves show pronounced negative differential resistance, with a peak-to-valley current ratio of 8.3 at 300 K. Good agreement is observed between measured and calculated peak current densities, consistent with light-hole tunneling through the confined InAs conduction-band state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346290
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  • 10
    Electronic Resource
    Electronic Resource
    Demonstration of resonant transmission in InAs/GaSb/InAs interband tunneling devices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2675-2677 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed a theoretical and experimental analysis of current transport in InAs/GaSb/InAs interband tunneling devices as a function of GaSb layer width. Our results demonstrate that current transport in these devices occurs not through simple ohmic conduction, as had been previously proposed, but via light-hole-like resonances in the GaSb valence band formed due to the imperfect matching of InAs conduction-band and GaSb valence-band wave functions at the InAs/GaSb interfaces. These resonances produce a strong dependence of the current-voltage characteristics on GaSb layer width that is both predicted theoretically and observed experimentally. Our results also suggest that coupling between InAs conduction-band and GaSb heavy-hole valence-band states is relatively unimportant in these devices. In addition, we have been able to obtain peak current densities of ∼9×104 A/cm2, significantly higher than any previously reported current densities for this structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104109
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