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  • 1
    Electronic Resource
    Electronic Resource
    Lattice contraction due to carbon doping of GaAs grown by metalorganic molecular beam epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1040-1042 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial layers of GaAs have been grown by metalorganic molecular beam epitaxy (MOMBE) with atomic carbon concentrations ranging from 4×1017 to 3.5×1020 cm−3. The dependences of GaAs lattice parameter and hole concentration on atomic carbon concentration have been determined from x-ray diffraction, Hall effect, and secondary-ion mass spectrometry measurements. For atomic carbon concentrations in excess of 1×1019 cm−3, the hole concentrations are less than the corresponding atomic carbon concentrations. Lattice parameter shifts as large as 0.2% are observed for carbon concentrations in excess of 1×1020 cm−3, which results in misfit dislocation generation in some cases due to the lattice mismatch between the C-doped epilayer and undoped substrate. Over the entire range of carbon concentrations investigated, Vegard's law accurately predicts the observed lattice contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102608
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  • 2
    Electronic Resource
    Electronic Resource
    Surface recombination current and emitter compositional grading in Npn and Pnp GaAs/AlxGa1−xAs heterojunction bipolar transistors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 641-643 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental study of current gain in Npn and Pnp GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBTs) with either compositionally graded or abrupt base-emitter heterojunctions is reported. In both Npn and Pnp device structures, linear compositional grading increases the amount of base current and lowers the transistor current gain from that observed in devices with abrupt base-emitter heterojunctions. Analysis of the dependence of the base current on emitter mesa size indicates that surface recombination dominates the Npn and Pnp base current in both the abrupt and graded devices. Taken together, these results suggest that the magnitude of the surface recombination current in Npn and Pnp GaAs/AlxGa1−xAs HBTs depends not only on the surface recombination velocity of the GaAs base free surface, but also on the energy barrier presented by the emitter to minority carriers attempting to enter the surface channel at the emitter mesa surface. Linear compositional grading of the emitter results in a lowering of this barrier and an increase in base current associated with carrier injection to the transistor surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100904
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of rapid thermal annealing temperature on the electrical properties of Be-implanted GaAs p-n junctions (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 2244-2246 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Planar, Be-implanted p-n junctions were fabricated in GaAs with rapid thermal annealing (RTA). Five second isochronal anneals over a temperature range of 600–1000 °C were studied with secondary ion mass spectrometry (SIMS), sheet resistance measurements, and variable diameter p-n junctions. Sheet resistance measurements indicate that a minimum RTA temperature of 600 °C is necessary for electrical activation of the implanted Be. SIMS analysis indicates that significant outdiffusion and surface evaporation of Be occur at all RTA temperatures in this range, while indiffusion of Be is insignificant for concentrations below 1×1018 cm−3. Forward bias current in diodes ranging in diameter from 10 to 1000 μm is dominated by surface recombination, rather than bulk space-charge recombination, over the entire 600–1000 °C temperature range. The magnitude of the surface recombination current is insensitive to the RTA temperature, which suggests that 600 °C RTA should be sufficient for the formation of satisfactory p-n junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99544
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  • 4
    Electronic Resource
    Electronic Resource
    Growth and diffusion of abrupt zinc profiles in gallium arsenide and heterojunction bipolar transistor structures grown by organometallic vapor phase epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4485-4493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth and diffusion of abrupt Zn profiles in undoped gallium arsenide (GaAs), silicon-doped GaAs, and heterojunction bipolar transistor structures grown by organometallic vapor phase epitaxy have been studied using secondary ion mass spectrometry depth profiling. The depth profiles indicate that abrupt (within 100 A(ring)) turn-on of Zn doping to levels approaching 1020 cm−3 are obtainable, while abrupt turn-off is limited to about two orders of magnitude due to dopant tailing toward the surface resulting from residual Zn in the reactor. The sharp diffusion fronts resulting from post-growth anneals indicate that the Zn diffusion coefficient has a concentration dependence. However, the diffusion of Zn at high concentrations appears to be inhibited by crystal defect kinetics resulting in a relatively concentration-independent Zn diffusion coefficient. The V/III growth ratio did not have an effect on Zn diffusion in undoped or silicon-doped GaAs. The diffusion of Zn in heterojunction bipolar transistor structures differs in that the diffusion of Zn into the GaAs collector is larger by an order of magnitude and decreases with an increase in V/III growth ratio. In addition, the diffusion of Zn into the aluminum gallium arsenide (AlGaAs) emitter is significantly lower and more effectively inhibited by an increase in V/III ratio than the diffusion of Zn into the GaAs collector.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340143
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  • 5
    Electronic Resource
    Electronic Resource
    Observation of radiative and nonradiative tunneling in GaAs/AlxGa1−xAs heterojunction bipolar transistors with compositionally graded base-emitter heterojunctions (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3282-3285 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparative experimental study of 77-K current gain and electroluminescent (EL) spectra in Npn GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBTs) with either compositionally graded or abrupt base-emitter heterojunctions is reported. Shifting-peak spectra associated with radiative tunneling of carriers into the base-emitter heterojunction space-charge region are observed to dominate the 77-K EL spectra of HBTs with linearly graded emitters. The 77-K EL spectra of the abrupt HBTs are characterized by a peak whose energy position is invariant with respect to base-emitter bias and corresponds to recombination of electrons diffusing across the HBT base. Comparison of EL peak intensity and transistor base current indicates that the graded HBT current gain at 77 K is determined by nonradiative tunneling of electrons and holes to deep levels at the base-emitter junction. The loss of minority carriers to radiative and nonradiative tunneling current mechanisms in the graded HBT causes the 77-K current gain of the graded HBT to be significantly lower than that of the abrupt HBT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342687
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  • 6
    Electronic Resource
    Electronic Resource
    Nonconventional electron diffusion current in GaAs/AlxGa1−xAs N-p-n heterojunction bipolar transistors with heavily doped base layers (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2530-2534 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of collector current density in a GaAs/AlxGa1−xAs N-p-n heterojunction bipolar transistor with a p-type base doping of 6×1018 cm−3 are compared with the conventional expression for electron transport by diffusion across the base layer. The experimental collector current density exceeds the conventional diffusion theory result by more than a factor of 4, even after band-gap shrinkage and bandtailing due to the heavy p-type base doping are taken into account in the determination of the thermal equilibrium electron density in the base. The potential necessity of retaining an additional term in the fundamental electron current density equation to account for the experimental collector current is stressed. The form of this additional current-driving term is exhibited equivalently in both an electron activity coefficient formalism and in terms of a spatial gradient of the conduction-band density of states. A conclusive assessment of the relative importance of this additional term will require a theoretical treatment of the influence of excess minority-carrier electron concentrations on the density of states and electron activity coefficient for excited p-type GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342774
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  • 7
    Electronic Resource
    Electronic Resource
    Direct molecular-beam epitaxial growth of ZnTe(100) and CdZnTe(100)/ZnTe(100) on Si(100) substrates (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 818-820 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial structures of ZnTe(100) and CdZnTe(100)/ZnTe(100) have been deposited by molecular-beam epitaxy onto Si(100) substrates misoriented from 0° to 8° towards the [011] direction. The films were characterized with x-ray diffraction, photoluminescence spectroscopy, optical microscopy, and stylus profilometry. Single-crystal CdZnTe(100) films comparable in structural quality to those obtained with growth on GaAs/Si composite substrates have been demonstrated on both 4° and 8° misoriented Si with the use of ZnTe buffer layers. X-ray rocking curves with FWHM less than 300 arcsec for ZnTe (400) and less than 160 arcsec for CdZnTe(400) have been obtained for as-grown films. Specular surface morphologies, superior to those obtained on GaAs/Si composite substrates, are also observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109918
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  • 8
    Electronic Resource
    Electronic Resource
    Comparative study of minority electron properties in p+-GaAs doped with beryllium and carbon (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 822-824 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Minority electron properties in p+-GaAs doped with beryllium (Be) and with carbon (C) are reported. Measurements of essentially identical responses for structures differing only in dopant element demonstrate that the diffusivity (Dn) and the diffusion lengths (Ln) are the same in p+-GaAs doped to ∼1019 cm−3 with Be- and C-dopants. Zero-field time-of-flight analysis yields Dn=35 cm2/s and internal quantum efficiency analysis yields Ln=2.4 μm, which implies a lifetime that is approximately at the estimated radiative limit. In addition, the majority Hall mobility was also found to be identical for the Be- and C-doped material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107756
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  • 9
    Electronic Resource
    Electronic Resource
    Valence-band-edge shift due to doping in p+ GaAs (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2126-2128 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Accurate knowledge of the shifts in valence- and conduction-band edges due to heavy doping effects is crucial in modeling GaAs device structures that utilize heavily doped layers. X-ray photoemission spectroscopy was used to deduce the shift in the valence-band-edge induced by carbon (p type) doping to a carrier density of 1×1020 cm−3 based on a determination of the bulk binding energy of the Ga and As core levels in this material. Analysis of the data indicates that the shift of the valence-band maximum into the gap and the penetration of the Fermi level into the valence bands exactly compensate at this degenerate carrier concentration, to give ΔEv =0.12±0.05 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104981
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  • 10
    Electronic Resource
    Electronic Resource
    Experimental observation of a minority electron mobility enhancement in degenerately doped p-type GaAs (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 536-538 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The variation of minority electron mobility with doping density in p+-GaAs has been measured with the zero-field time-of-flight technique. The results from a series of nine GaAs films doped between 1×1018 and 8×1019 cm−3 show the mobility decreasing from 1950 cm2 V−1 s−1 at 1×1018 cm−3 to 1370 cm2 V−1 s−1 at 9×1018 cm−3. For the doping range 9×1018–8×1019 cm−3, the decreasing trend in mobility is reversed. The measured mobility of 3710 cm2 V−1 s−1 at 8×1019 cm−3 is about three times higher than the measured value at 9×1018 cm−3. These results confirm and extend recent transistor-based measurements and are in accord with recent theoretical predictions that attribute the increase in minority electron mobility in p+-GaAs to reductions in plasmon and carrier-carrier scattering at high hole densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109997
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