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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical and experimental study of the longitudinal uniaxial stress dependence of I-V characteristics in GaAs-AlxGa1−xAs-GaAs heterojunction barriers (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6360-6367 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tunneling and thermionic emission through n+-GaAs–i-AlxGa1−xAs–n-GaAs heterojunction barriers are studied as a function of temperature from 77 to 200 K and as a function of externally applied uniaxial stress up to 10 kbar. A procedure to extract parameters for theoretical calculations is also proposed. The parameters extracted from the I-V characteristics of these heterostructures grown on (100) GaAs substrates with different aluminum mole fractions from 0.3 to 0.8 and thicknesses from 300 to 400 A(ring) agree well with those of previous reports. The dependence of the I-V characteristics on uniaxial stress in the 〈100〉 direction perpendicular to the heterojunction plane has also been measured. The experimental results show good agreement with theoretical calculations assuming there is a linear stress-dependent decrease of the energy-band edges of the longitudinal X valleys (Xl) in AlGaAs with respect to the Γ valley in GaAs. The slope of the decrease is found to be 14±2 meV/kbar. This results in an X-valley shear deformation potential of 9.6±1.8 eV, which is believed to be the most accurate measured value to date.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345157
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  • 2
    Electronic Resource
    Electronic Resource
    Noise spectroscopy of deep level (DX) centers in GaAs-AlxGa1−xAs heterostructures (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1541-1548 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the generation-recombination noise from the donor-related DX centers in current biased GaAs/AlxGa1−xAs heterostructures from 1 Hz to 25 kHz and from 77 to 330 K. A significant noise contribution from these traps is observed even at Al mole fractions below 0.2, where the trap level is resonant with the conduction band. The activated behavior of the noise spectrum from this resonant level is very similar to that observed at higher Al mole fractions, when the level lies deep in the fundamental gap. This result can be predicted, based on the recently elucidated relationship of the trap level to the band structure of AlxGa1−xAs. In accordance with other experimental results, the noise spectra demonstrate that the emission and capture kinetics of the level are unperturbed by its resonance with the conduction band. We briefly discuss some implications of these results for heterostructure transistor design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339938
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  • 3
    Electronic Resource
    Electronic Resource
    DX centers in AlGaAs p-n heterojunctions and heterojunction bipolar transistors (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3234-3236 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: DX centers are found to cause the capacitance of an AlGaAs/GaAs p-n heterojunction at 77 K to behave like that of a p-i-n diode. Exposure to light causes the capacitance to behave like a normal p-n junction. It is argued that the presence of DX centers has only a small effect on the switching properties heterojunction bipolar transistors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339326
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  • 4
    Electronic Resource
    Electronic Resource
    Energy band alignment in GaAs:(Al,Ga)As heterostructures: The dependence on alloy composition (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 200-209 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band alignment in GaAs:(Al,Ga)As heterostructures has been investigated over the full range of alloy composition. The valence-band discontinuity ΔEv is determined by measuring the activation energy for thermionic emission of holes from p-GaAs over an undoped, square (Al,Ga)As barrier. The use of p-type structures to measure ΔEv circumvents a number of complications involved in the measurement of ΔEc. The parameters required for analysis are determined by different measurements on the same structures and the analysis is performed so that the activation energy, extrapolated to zero bias, yields ΔEv directly. It is found that ΔEv is a linear function of the aluminum mole fraction xAl@B: ΔEv (approximately-equal-to)0.55xAl (eV) (0≤xAl≤1). The validity of these data is supported by measurements of ΔEc in the direct band-gap regime, where complementary values of ΔEv and ΔEc add up to the expected band-gap difference. This relationship provides a simple description of the full band alignment in this heterosystem and should prove valuable as a test of the various heterojunction lineup theories. Moreover, these measurements have a number of important consequences, particularly from the viewpoint of heterojunction devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336864
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  • 5
    Electronic Resource
    Electronic Resource
    Energy band-gap discontinuities in GaAs:(Al,Ga)As heterojunctions (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 484-487 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The measurement of the energy band discontinuities in GaAs:(Al,Ga)As heterostructures is described. These values are deduced from the activation energy governing current transport in the direction perpendicular to the heterojunction interface. Using complementary structures (fabricated with an Al mole fraction of (approximately-equal-to)0.38), we study both electron and hole transport to independently measure the conduction and valence-band discontinuities respectively. The results obtained are self-consistent and indicate that the total band-gap difference distributes approximately in the ratio 60:40 between the conduction band and valence band. Measurement of the conduction-band discontinuity for an Al mole fraction of (approximately-equal-to)0.24 yields a similar ratio. Preliminary measurements of the valence-band discontinuity in structures fabricated using (Al,Ga)As with an indirect band gap (Al mole fraction of (approximately-equal-to)0.60) are also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334778
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature dependence of carrier density in depleted epitaxial layers deposited on semi-insulating substrates (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1565-1569 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have calculated the temperature dependence of the carrier density in epitaxial layers of semiconductors deposited on semi-insulating substrates when the potentials at the surface and the substrate interface are pinned. The results of these calculations are compared to experiments on thin, nominally undoped p-type layers of GaAs deposited epitaxially on EL2-dominated substrates. The theory predicts that as the temperature is lowered to some critical value the depletion layers at the edges of the epilayer overlap for thin, lightly doped samples. Below this value the carrier density decreases exponentially with inverse temperature with an activation energy which depends on the surface and interface potentials, as well as on the dopant concentration and the width of the layer. This activation energy can be derived analytically for strong depletion. In the intermediate range between negligible and complete depletion of the layer the carrier density must be obtained by numerical methods, and we present the results of such a calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349518
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  • 7
    Electronic Resource
    Electronic Resource
    Resonant indirect Fowler–Nordheim tunneling in Al0.8Ga0.2As barrier (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 266-268 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oscillatory current-voltage characteristics of n+-GaAs/semi-insulating Al0.8Ga0.2As/nGaAs heterojunction barriers (400 A(ring) thick) grown by molecular beam epitaxy on n+-GaAs (100) substrates are observed at 4 K when the heterostructures are placed under the transverse uniaxial stress along 〈011〉 direction (perpendicular to current direction) above 4 kbar. We attribute these oscillations to the resonant indirect Fowler–Nordheim tunneling via 〈011〉 oriented transverse X valleys, where the change of wave vector is required for tunneling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104684
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  • 8
    Electronic Resource
    Electronic Resource
    Threshold shifting in pseudomorphic semiconductor-insulator-semiconductor heterostructure field-effect transistors (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2285-2287 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudomorphic (In,Ga)As layers are used in GaAs-based semiconductor-insulator- semiconductor (SIS) structures to shift the threshold voltage from the natural, near-zero value. The threshold voltage is shifted positively for (In,Ga)As gate layers, and negatively for (In,Ga)As channel layers, by the (In,Ga)As/GaAs conduction-band offset. The thermionic and field emission barrier heights agree with shifts obtained in capacitance-voltage characteristics. The structures withstand implant activation anneals, establishing a simple technology to create either enhancement or depletion-mode devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104900
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  • 9
    Electronic Resource
    Electronic Resource
    Thermally stable ohmic contacts to n-type GaAs. VIII. Sputter-deposited InAs contacts (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2475-2481 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical properties and microstructure of InAs ohmic contacts to n-type GaAs, prepared by sputter-depositing a single target, were studied by measuring the contact resistance (Rc) by the transmission line method and analyzing the interfacial structure by x-ray diffraction and cross-sectional transmission electron microscopy. Current-voltage measurement of an as-deposited InAs/W contact showed Schottky behavior, where the W layer was used as a cap layer. The InAs layer had an amorphous structure and a uniform oxide layer was observed at the InAs/GaAs interface. Even after annealing at 800 °C, ohmic behavior was not obtained in this contact because the intervening oxide layer prevented the InAs and GaAs interaction. By adding Ni to the InAs/W contacts (where Ni was deposited by an evaporation method), the interaction between the InAs and the GaAs was enhanced. Nickel interacted with As in the InAs layer and formed NiAs phases after annealing at temperature above 600 °C. The excess In in the InAs layer reacted with the GaAs substrate, forming InxGa1−xAs phases which covered about 80% of the GaAs interface. The Rc values of ∼0.4 Ω mm were obtained for InAs/Ni/W and Ni/InAs/Ni/W contacts at annealing temperatures in the range of 750–850 °C. These contacts contained only high melting point compounds and the contacts were stable during annealing at 400 °C for more than 100 h after ohmic contact formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346509
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  • 10
    Electronic Resource
    Electronic Resource
    The capture barrier of the DX center in Si-doped AlxGa1−xAs (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 4786-4797 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of the capture barrier for the DX center in Si-doped AlxGa1−xAs as a function of the alloy composition. A model of the capture process which requires a distribution of capture barrier heights has been fit to the data for samples with x=0.35. A simple technique is used to extract the average capture barrier height from data for samples with AlAs mole fraction ranging from x=0.27 to x=0.55. The barrier height varies strongly with the composition and has a minimum at x=0.35. The implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338981
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