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  • 1
    Electronic Resource
    Electronic Resource
    Electron tunneling spectroscopy and defects in GaAs/AlGaAs/GaAs heterostructures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5333-5336 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron tunneling spectroscopy has been used to study the phonon modes of the GaAs electrode and the AlGaAs barrier of single barrier GaAs/AlGaAs/GaAs heterostructures. The barriers were spiked doped with Si or Be to determine whether defects or impurities in the barrier have an effect on the measured line shapes. The phonon line shapes and intensities have been observed to change after shining light on the devices to photoionize defects in the barrier. The results demonstrate that the charge state of defects in a heterostructure barrier can affect the interaction between a tunneling electron and the phonon modes of a tunnel barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351968
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  • 2
    Electronic Resource
    Electronic Resource
    Residual defects in AlGaAs co-implanted with Be and P or As (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5090-5094 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep-level transient spectroscopy (DLTS) and capacitance-voltage (C-V) measurements have been used to study the residual defects in n-type AlGaAs co-implanted with Be and either As or P. The co-implant procedure is being studied as a method for limiting Be diffusion during the rapid thermal annealing process used to activate the Be. The only defect found in the upper half of the band gap by DLTS measurements between 10 and 450 K has an activation energy of 0.88 eV. This defect undergoes photocapacitance quenching, which together with its activation energy suggests that it is similar to the EL2 defect found in GaAs. In an analysis of high-temperature C-V data, the defect manifests itself as a peak in the donor concentration. The donor concentration data were modeled by doing a double integration of Poisson's equation assuming a Gaussian defect distribution and a uniform shallow donor distribution. This analysis indicates that the center of the Gaussian defect distribution is near the peak in the P or As distribution and that the peak concentrations are about 1×1017 defects cm−3 for the higher P and As fluences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347072
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  • 3
    Electronic Resource
    Electronic Resource
    Deep level transient capacitance measurements of GaSb self-assembled quantum dots (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5843-5849 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep level transient spectroscopy (DLTS) measurements have been made on GaAs n+p diodes containing GaSb self-assembled quantum dots and control junctions without dots. The self-assembled dots were formed by molecular beam epitaxy using the Stranski–Krastanov growth mode. The dots are located in the depletion region on the p side of the junction where they act as a potential well that may capture and emit holes. Spectra recorded for temperatures between 77 and 440 K reveal several peaks in diodes containing dots. A control sample with a GaSb wetting layer was found to contain a single broad high temperature peak that is similar to a line found in the GaSb quantum dot samples. No lines were found in the spectra of a control sample prepared without GaSb. DLTS profiling procedures indicate that one of the peaks is due to a quantum-confined energy level associated with the GaSb dots while the others are due to defects in the GaAs around the dots. The peak identified as a quantum-confined energy level shifts to higher temperatures and its intensity decreases on increasing the reverse bias. The activation energy for the quantum-confined level increases from 400 meV when measured at a low reverse bias to 550 meV for a large reverse bias. Lines with activation energies of 400, 640, and 840 meV are associated with defects in the GaAs based on the bias dependence of their peak positions and amplitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1318391
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  • 4
    Electronic Resource
    Electronic Resource
    Barrier roughness effects in resonant interband tunnel diodes (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6177-6181 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Peak current densities of InAs/AlSb/GaSb/AlSb/InAs resonant interband tunneling diodes (RITD) grown by molecular beam epitaxy have been measured as a function of the growth temperature. The growth procedures were designed to produce nominally identical AlSb tunneling barriers. The variations observed in the peak current for positive bias are consistent with the barrier on the substrate side of the RITD becoming effectively thicker for diodes grown at high temperatures. Plan-view in situ scanning tunneling microscopy (STM) measurements indicate that smoother AlSb barriers are grown at high temperature. The growth temperature dependence of the peak current density and STM results are consistent, because tunneling is highly dependent on barrier thickness. While the high and low temperature growths were designed to have the same barrier thickness, the large current flowing through the thin areas of a rough barrier result in an effectively thinner barrier compared to the smooth one. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415539
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  • 5
    Electronic Resource
    Electronic Resource
    Operation and design of metal-oxide tunnel transistors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5021-5031 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current–voltage (I–V) characteristics in the ballistic limit of metal-oxide tunnel transistors are calculated as a function of temperature, potential barrier height, gate insulator thickness, aspect ratio, and oxide-channel shape. The saturation (‘knee') point and three modes of current transport across the device are discussed. For a given aspect ratio, the output impedance improves with increase in tunnel-oxide width, accompanied by slight decrease of gate transconductance. The net result is a significant improvement in the transistor gain. The gate transconductance improves with decrease in gate-insulator thickness, while approximately maintaining the output impedance. The net result is also a significant improvement in the transistor gain. Thus for a given aspect ratio, further device optimization to increase the transistor gain can be carried out by either increasing the tunnel oxide width or decreasing the gate insulator thickness. In practice, one preferably does both. A numerical study of the device performance of tapered-oxide devices is undertaken. We find that uniform-oxide channel design is generally superior to tapered-oxide channel designs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368749
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  • 6
    Electronic Resource
    Electronic Resource
    Phonons in self-assembled (In,Ga,Al)Sb quantum dots (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 958-960 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum dots of InSb, GaSb, and AlSb were grown on GaAs substrates by molecular beam epitaxy and characterized by atomic force microscopy and Raman spectroscopy. There is a clear correlation between the observation of quantum dots by atomic force microscopy and a phonon mode at an energy a few wavenumbers below the longitudinal optic phonon energy for thick (In,Ga,Al)Sb layers. In the case of nominally AlSb quantum dots, a two-mode behavior is observed and attributed to the segregation of Ga into the AlSb during growth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116111
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxial growth of InSb, GaSb, and AlSb nanometer-scale dots on GaAs (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 505-507 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin layers of InSb, GaSb, and AlSb were grown on GaAs substrates by molecular beam epitaxy. Atomic force microscopy was used to examine surface morphology as a function of growth temperature and monolayer coverage. For each material, conditions were found which resulted in Stranski–Krastanov growth with the strain-induced formation of nanometer-scale dots. Relatively uniform distributions of dots form in a temperature window near the congruent sublimation temperature for both InSb and GaSb. In the case of InSb, deposition of 2 monolayers at 430 °C produced a surface with 3×109/cm2 dots with heights of 58±5 A(ring) and diameters of 600±50 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116381
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  • 8
    Electronic Resource
    Electronic Resource
    Dependence of gate control on the aspect ratio in metal/metal-oxide/metal tunnel transistors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1133-1139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The design criteria for large transconductance/high output impedance or high-gain operation of metal-oxide tunneling transistors is given. The dependence of the gate control on the aspect ratio of thickness to width of the tunneling oxide is investigated by computer simulation. This device structure can only operate similar to conventional semiconductor transistors for aspect ratio considerably less than one. It ceases to function as a transistor for larger aspect ratio due to insufficient penetration of the gate control field into the tunneling oxide. To demonstrate this, the current–voltage characteristics are computed for aspect ratios equal to 7/30, 1, 21/10, and the different tunneling-current behaviors compared with our experimental results on Ti/TiOx/Ti and Nb/NbOx/Nb tunnel transistors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368114
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  • 9
    Electronic Resource
    Electronic Resource
    Resonant interband tunnel diodes with AlGaSb barriers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5791-5793 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The peak current density of InAs/AlSb/GaSb/AlSb/InAs resonant interband tunneling diodes has been enhanced by replacing the AlSb barriers with Al1−xGaxSb that has a narrower band gap. The devices were grown by molecular beam epitaxy and tested at room temperature. Diodes with nominally identical 7-ML-thick ternary alloy barriers with x=0.35 are found to have peak current densities three times larger than those with AlSb barriers. The peak-to-valley current ratio decreases by only one third from 18 for the AlSb diodes to 12 for diodes with the ternary alloy barriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1365940
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  • 10
    Electronic Resource
    Electronic Resource
    Metastable defects in Be-doped AlxGa1−xAs (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4828-4831 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep-level transient spectroscopy has been used to study metastable defects in Be-doped Alx Ga1−x As grown by molecular-beam epitaxy. The metastability manifests itself by the appearance of different spectra depending upon whether the sample is cooled from a high temperature with zero bias or a reverse bias applied to it. The defects are found in concentrations of 1015 cm−3 in a sample doped with 1018 Be cm−3 and in much lower concentrations in a 1017 Be cm−3 sample. Isochronal annealing experiments indicate that the defect is multistable and that it is best modeled as a mobile interstitial which can reside at several sites near an acceptor. The activation energies for these defects are between 0.2 and 0.5 eV above the valence band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343216
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