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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4286-4289 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Capacitance-voltage measurements were performed on the InAs/AlSb/GaSb interband tunneling diode at various frequencies. Theoretical analyses using a self-consistent Schrödinger–Poisson solver were found in agreement with the experimental results under the forward-bias condition. The quantization energy of each subband of the electron in the InAs accumulation region is used to predict the tunneling current cutoff voltage in agreement with that of the current-voltage measurements. Therefore, the cutoff of the interband tunneling process is mainly caused by the crossover of the electron subband energy in the InAs conduction band with respect to the valence band of the GaSb electrode due to the increased external bias voltage.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3451-3455 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dependence of the interband tunneling current on AlSb barrier widths is studied in the InAs/AlSb/GaSb single-barrier diode structures. The experimental results show that the peak current density displays an exponential dependence on the barrier width. The Wentzel-Kramers-Brillouin approximation combined with the k⋅p two-band model were used in analyzing the energy level in the AlSb barrier through which the peak tunneling currents occur. The energy level thus obtained (0.48±0.10 eV above the valence band edge of the AlSb) agrees with the valence-band offset (0.40±0.15 eV) between the AlSb and the GaSb obtained by x-ray photoemission measurement reported by Gualtieri et al. [Appl. Phys. Lett. 49, 1037 (1986)]. By adjusting the barrier width properly, we obtained a high peak current density of 24 kA/cm2 (with a peak-to-valley ratio of 1.4) and a high peak-to-valley ratio of 4.5 (with a peak current density of 3.5 kA/cm2) at room temperature. In addition, the peak-current voltages for different AlSb barrier widths were calculated and compared with the measured results.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2997-3000 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose and demonstrate a new GaSb/AlSb/GaSb/AlSb/InAs double-barrier interband tunneling diode with a peak-current density as high as 7.6 kA/cm2 and a peak-to-valley current ratio of 5. In this device, the electrons in the InAs conduction band can resonantly tunnel through the AlSb/GaSb/AlSb double barrier into the GaSb valence band. By narrowing the GaSb well width from 65 to 30 A(ring), a drastic reduction of the tunneling current was found experimentally. This reduction is interpreted as evidences of the effect of the interband resonant tunneling process and the role of the light hole in the GaSb valence band. In addition, compared with the InAs/AlSb/GaSb/AlSb/InAs tunneling structure, a twice larger peak current density was obtained in the proposed structure which is attributed to a larger density of states of the GaSb light hole valence band compared with that of the InAs conduction band.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2540-2542 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied experimentally the effect of several electron launcher structures on AlAs/GaAs double barrier resonant diodes (RTDs). The experimental results show that a linearly graded AlGaAs launcher structure improves the tunneling current by presumably removing the hump in the conduction band caused by the space charges near the n-i junction in the spacer layer. Peak current densities as high as 170 kA/cm2 with a peak-to-valley current ratio of 3.2 were obtained from these graded launcher RTDs. Compared with the conventional RTD, the graded launcher gives a 50% improvement in the peak current density while reducing the peak-current voltage by 40% and maintaining a similar peak-to-valley current ratio.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Until now, the origin of hard magnetic properties of rapidly quenched Nd-Fe-B alloys with lower Nd concentration is not clear. In this paper, the phase compositions of rapidly quenched Nd4Fe77.5B18.5 alloys annealed under different conditions have been studied by using zero-field spin-echo nuclear magnetic resonance (NMR) and Mössbauer effect (ME) techniques. It is found that there exists a certain amount of Nd2Fe14B phase in the samples annealed at 960 °C and ingot alloy, which have poor hard magnetic properties; while, the sample annealed under optimal condition consists only of bct-Fe3B as the main phase and a small amount of a-Fe. However, the ME result indicates that about 5 at. % Fe atoms in FeIII (8 g) site of bct-Fe3B have been replaced by Nd atoms; the NMR result demonstrates that 11B NMR spectrum is the characteristic peak of bct-Fe3B, but it broadens asymmetrically to the high frequency side, which is due to the bct-Fe3B influenced by Nd atoms. The amplitude of radio frequency (rf) excitation field required to get the maximum 11B spin-echo signal from bct-Fe3B in the sample annealed at 839 °C is only about one third as much as that required to excite the 11B in the bct-Fe3B influenced by Nd atoms in the sample annealed at 670 °C for a short time, which implies the latter has a larger coercivity field than the former. It is concluded that the origin of hard magnetic properties of Nd4Fe77.5B18.5 alloy is not related to the 2:14:1 phase, but to the change of bct-Fe3B itself.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 754-756 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A shallow Pd/Ge/Ti/Pt/ohmic contact for both n- and p-GaAs has been investigated. The contacts were rapid thermally annealed in N2 for 15 s at temperatures from 350 to 550 °C. The lowest average specific contact resistances were 4.7×10−7 and 6.4×10−7 Ω cm2 for the n- and p-GaAs, respectively, when the n-GaAs was doped with Si to 2×1018 cm−3 and the p-GaAs was doped with carbon to 5×1019 cm−3. Electrical measurements and Auger depth profiles showed that the contacts were stable as they remained ohmic after an anneal at 300 °C for 20 h for both n- and p-GaAs. The p contact is more stable than the n contact at the higher temperatures where there is more As outdiffusion as determined by Auger depth profiles. Transmission electron microscopy showed that the interfaces between the p-GaAs and the contacts were smooth for both as-grown and annealed samples, and no oxides were detected.
    Type of Medium: Electronic Resource
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3040-3043 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated an InAs/AlSb/GaSb single-barrier interband tunneling diode by molecular beam epitaxy. In this structure, a large tunneling current can be obtained by taking the advantage of the large heterojunction-conduction band to valence band overlap (0.15 eV) between InAs and GaSb which offers flexible designs of the AlSb barrier thickness and the doping concentrations. We have obtained a negative differential resistance with a peak-to-valley current ratio as high as 4.7 and a peak current density of 3.5 kA/cm2 at room temperature with a 1.5-nm-thick AlSb barrier. The current transport mechanism in this tunneling structure will be discussed according to the I-V characteristics as a function of temperature.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1503-1510 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystal CuIn3Se5 epitaxial films have been synthesized on GaAs(001) by a hybrid sputtering and evaporation technique. The microstructure, microchemistry, and selected electrical and optical properties of the films have been investigated by scanning electron microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy, cathodoluminescence, optical absorption and reflection, and four-point probe resistivity measurements. The results showed that the CuIn3Se5 crystals have an ordered point defect structure, a band gap of ≥1.18 eV, an optical absorption coefficient of about 15 000 cm−1 at a photon energy of 1.35 eV, and a film resistivity of (approximately-greater-than)105 Ω cm. The results suggest the presence of band tails giving rise to subgap radiative recombination and absorption. Antiphase domain boundaries, stacking faults, and nanotwins were observed in the epitaxial layers and were reduced in number by rapid thermal annealing.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 708-715 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cu clusters of nanometer dimensions were created by implantation of Cu ions into pure fused silica substrates at energies of 160 keV. The sizes and size distributions of the Cu clusters were measured by transmission electron microscopy, and were found to be determined by the ion-beam current during implantation. Optical-absorption spectra of these materials show the size-dependent surface plasmon resonance characteristic of noble-metal clusters. There are also significant size-dependent effects in both the nonlinear index of refraction and two-photon absorption coefficients. The distinctive variations in linear and nonlinear optical properties with Cu nanocluster sizes and size distributions affords potentially interesting possibilities for using these materials in nonlinear optical devices.
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