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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of heavily carbon-doped GaAs grown by metalorganic chemical vapor deposition and metalorganic molecular beam epitaxy (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 981-987 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carbon-doped GaAs with carbon concentrations ranging from 2×1017 cm−3 to 2.6×1020 cm−3 has been characterized by variable temperature Hall effect measurements, secondary ion mass spectrometry (SIMS), and double-crystal x-ray diffraction (DCXD). The samples studied were grown by metalorganic chemical vapor deposition (MOCVD) and by metalorganic molecular beam epitaxy (MOMBE). The hole mobility is dominated by degenerate conduction for hole concentrations ≥1×1019 cm−3, and the 77 K resistivity is typically 30%–35% lower than at 300 K in these samples. The mobilities of C-doped p+-GaAs are found to be significantly higher than for Zn- or Be-doped p+-GaAs for doping concentrations in excess of 2×1018 cm−3. The maximum achievable hole mobilities for C-doped material grown by the two techniques are nearly identical, indicating that neither MOCVD nor MOMBE has an inherent advantage over the other for producing low-resistivity p-type GaAs. SIMS analysis and Hall effect measurements reveal that the total carbon concentration, [C], is higher than the as-grown hole concentration, p, in the most heavily doped samples. DCXD measurements show general agreement with the lattice mismatch predicted by Vegard's law. However, for [C](approximately-greater-than)1020 cm−3 a discrepancy between the predicted and measured mismatch suggests that partial lattice relaxation or the presence of interstitial carbon may need to be considered in order to adequately describe the lattice contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351776
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  • 2
    Electronic Resource
    Electronic Resource
    Hall-effect measurement and a defect model analysis of surface-potential changes in GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7635-7637 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, increases of the surface potential in n-type epitaxial GaAs after NH4OH treatment studied using Hall-effect measurements, were reported. In this work, complementary results for p-type samples show decreases in band bending, again in agreement with the predictions of the advanced unified defect (AUD) model for the surface-interface states. From this and other data, a working mathematical model based on the AUD model is developed. Probable values for its parameters are determined which suggest a physically reasonable mechanism to explain the surface-potential changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350364
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  • 3
    Electronic Resource
    Electronic Resource
    Growth-induced shallow acceptor defect and related luminescence effects in molecular beam epitaxial GaAs (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 741-754 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a study of a defect responsible for the "g'' bound exciton line at 1.5112 eV that is frequently detected in photoluminescence spectra of GaAs grown by molecular beam epitaxy (MBE). A direct correlation has been observed between this line and a transition at 1.4946 eV, which is shown to result from a conduction band-to-acceptor recombination involving a shallow, unidentified acceptorlike defect that is labeled "A.'' The activation energy of the defect is 24.8±0.2 meV, about 1.7 meV lower than that of CAs acceptor. Upon hydrogenation the defect is passivated more extensively than any known shallow acceptor species in GaAs. This result is analyzed in terms of a passivation model, from which it can be inferred that the A defect is not due to a simple substitutional Group II impurity on a Ga site. Incorporation of the A defect strongly affects the luminescence properties of the material. An almost complete quenching of the donor-bound exciton lines, profound changes in the line shape and relative intensity of the free exciton recombination, and appearance of a sharp transition of unknown origin at 1.5138 eV were observed with increasing defect concentration. Apparently "donorless'' low temperature exciton recombination spectra are reported for defect-rich p-type MBE GaAs layers with donor concentrations as high as 7×1014 cm−3 and compensation ratios of ∼0.3. The dependence of the defect incorporation on MBE growth parameters is discussed. The feasibility of MBE growth of high purity, nearly shallow defect-free p-type GaAs layers at marginally As-stabilized surface conditions over an about 1–5 μm/h range of deposition rates is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346779
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  • 4
    Electronic Resource
    Electronic Resource
    Layer intermixing in heavily carbon-doped AlGaAs/GaAs superlattices (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5615-5620 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interdiffusion of Al and Ga in heavily C-doped Al0.3Ga0.7As/GaAs superlattice (SL) structures has been investigated quantitatively for a variety of ambient and surface encapsulation conditions. High-resolution photoluminescence (PL) at T=1.7 K was employed to evaluate the extent of layer intermixing after 24-h anneals at 825 °C. From the shifts to higher energies of the PL peaks due to n=1 electron-to-heavy hole transitions in the quantum wells of the annealed SLs relative to the position of this peak in the as-grown crystal, approximate Al-Ga interdiffusion coefficients (DAl-Ga) have been determined for different annealing conditions. For all encapsulants studied the interdiffusion in C-doped crystals is accelerated with increasing As4 pressure in the annealing ampoule. This result disagrees with previously observed trends for Group II-doped p-type structures, which have led to the charged point-defect model (Fermi-level effect) of Al-Ga interdiffusion. The Si3N4 cap has provided the most effective surface sealing against ambient-stimulated layer interdiffusion, and yielded DAl-Ga≈1.5−3.9×10−19 cm2/s. The most extensive layer intermixing has occurred for uncapped SL annealed under As-rich ambient (DAl-Ga≈3.3×10−18 cm2/s). These values are up to ∼40 times greater than those previously reported for nominally undoped AlxGa1−xAs/GaAs SLs, implying that the CAs doping slightly enhances host-atom self-diffusion on the Group III sublattice, but significantly less than predicted by the Fermi-level effect. The discrepancies between the experimental observations and the model, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346973
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogenation of Si- and Be-doped InGaP (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5866-5870 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on the hydrogenation of Be-doped (p-type) and Si-doped (n-type) In1−xGaxP epitaxial layers grown lattice matched to GaAs (x ∼ 0.5). Low-temperature (1.7 K) photoluminescence, electrochemical carrier concentration profiling, and scanning electron microscopy are used to study the effects of hydrogenation on carrier recombination, carrier concentration, and surface morphology. Hydrogenation is found to passivate Si donors and Be acceptors and to improve photoluminescence efficiency, but causes mild surface damage. The carrier concentration following hydrogenation is found to be lowest in acceptor-doped material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346961
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  • 6
    Electronic Resource
    Electronic Resource
    Species dependence of passivation and reactivation of acceptors in hydrogenated GaAs (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3554-3563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of passivation and light-induced reactivation of acceptors in high-purity hydrogenated GaAs are investigated with low-temperature photoluminescence. The effectiveness of both processes has been found to be strongly dependent on the chemical identity of acceptor species, thus allowing a qualitative assessment of the relative stability of different acceptor-hydrogen passivating complexes in p-type hydrogenated GaAs. Efficient neutralization of acceptors in high-purity n-type hydrogenated GaAs is also reported, in contradiction with results of recent studies on heavily doped materials where passivation of minority dopants was not observed. The implications of these experimental data on theoretical models of the [AV:acceptor passivation mechanism are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346315
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  • 7
    Electronic Resource
    Electronic Resource
    Degradation of mobility in neutron irradiated GaAs by the increased scattering from multiply charged ionized defects (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3734-3739 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mobility changes were measured at temperatures from 15 to 305 K in n-GaAs van der Pauw samples irradiated by fast reactor neutrons. The inverse mobility values, obtained from the variable temperature Hall measurements were fitted using the relation μ−1=AT−3/2+BT3/2. The inverse mobility was found to increase as a result of neutron irradiations over the whole range of temperature; the increase is attributed to the increased scattering from neutron induced charged defects. The values of A found by the least square fitting were used to estimate the increased scattering effect from neutron-induced ionized defects after each step of irradiation. It is concluded that in order to explain the experimental results presented here, the creation of multiply charged defects must be considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352904
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  • 8
    Electronic Resource
    Electronic Resource
    Zero-field time-of-flight characterization of minority-carrier transport in heavily carbon-doped GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7471-7477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Minority-carrier electron-diffusion coefficients and lifetimes have been measured in heavily doped p-type GaAs using the zero-field time-of-flight (ZFTOF) technique. The materials studied included C-doped GaAs grown by molecular-beam epitaxy (MBE) using graphite as the dopant source, C-doped GaAs grown by metalorganic chemical-vapor deposition (MOCVD) using CCl4 as the dopant source, and Be-doped GaAs grown by MBE. Room-temperature photoluminescence intensity measurements were made on the structures and the results are compared with ZFTOF measurements of lifetime. The graphite-doped material (p∼1019 cm−3) exhibited diffusion lengths of less than 1000 A(ring). MOCVD-grown C-doped GaAs, which was optimized by adjusting the growth conditions to maximize the room-temperature photoluminescence intensity, had diffusion lengths comparable to those measured in Be-doped GaAs for hole concentrations of 1×1019 and 5×1019 cm−3. Comparison of photoluminescence intensities also suggests that addition of In to very heavily doped MOCVD-grown GaAs (p(approximately-greater-than)1020 cm−3) to eliminate the lattice mismatch with respect to the substrate does not result in an improvement in lifetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353991
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of the thermal dissociation of PH3 and NH3 using quadrupole mass spectrometry (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 8025-8030 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal dissociation of PH3 and NH3 injected through a Ta-based high-pressure gas-injection cell were studied. Using a quadrupole mass spectrometer, the Ta was found to effectively dissociate the PH3 into primarily P2, P4, and H2 molecules with an injector temperature as low as 550 °C. The introduction of NH3 through this same injector resulted in dissociation into N2 and H2 for an injector temperature greater than 900 °C. When NH3 and PH3 were coinjected, again P2, P4, N2, and H2 were the primary molecules produced; however, an additional dimer, PN, was also detected. The PN concentration was maximum at a cell temperature of 700 °C. This dimer was found to be an effective source for introducing nitrogen as an isoelectronic trap in GaP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347447
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  • 10
    Electronic Resource
    Electronic Resource
    The gas source molecular beam epitaxial growth of AlxGa1−xP on (100) GaP (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2133-2139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of AlxGa1−xP for Al mole fractions between 0 and 1 has been achieved on (100) GaP substrates using gas source molecular beam epitaxy with elemental Ga and Al, and P2 cracked from PH3 as the source materials. The observed reflection high energy electron diffraction pattern of the GaP surface indicates that an exponential increase in the incident P2 flux is required to maintain good morphology beyond 690 °C. This temperature was found to correspond closely to the congruent vaporization temperature of Ga from the growth surface. The addition of Al on the surface was found to substantially increase the Ga congruent vaporization temperature from the GaP surface. The growth rates for AlxGa1−xP as a function of growth temperature between 600 and 750 °C were determined by transmission electron microscopy. Using elemental Si as an n-type dopant, free electron concentrations as high as 1.65×1019 cm−3 in GaP and 1.5×1019 cm−3 in Al0.28Ga0.72P were achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346569
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