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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Current-voltage and capacitance-voltage behavior of high-resistivity (AlxGa1−x)yIn1−yP on GaAs (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 650-652 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Unintentionally doped layers of (AlxGa1−x)y In1−y P with energy gaps of approximately 2.0 eV were grown lattice matched to GaAs by organometallic vapor phase epitaxy. These layers were high resistivity. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were made on Cr/Au (AlxGa1−x)y In1−y P-GaAs metal-insulator-semiconductor capacitors. These measurements gave a ln I variation with V1/2 as observed for insulators such as Si3N4 on Si. This conduction behavior is characteristic of the Frenkel–Poole effect which is the electric field enhanced thermal excitation of trapped electrons into the conduction band. The C-V measurements were similar to the small hysteresis behavior of high-resistivity oxygen-doped AlxGa1−xAs on GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100907
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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
    Correlation of substitutional hydrogen to refractive index profiles in annealed proton-exchanged Z- and X-cut LiNbO3 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2697-2708 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Previous disagreements concerning a linear correlation between the hydrogen (H) concentration and the extraordinary refractive index ne in proton-exchanged lithium niobate (LiNbO3) have been resolved by partitioning the total H into optically active substitutional H and optically inactive interstitial H. The H and Li spatial variations in both Z- and X-cut crystals were determined by secondary-ion-mass spectrometry (SIMS) with a quantitative evaluation in atoms/cm3. These samples were proton exchanged in neat benzoic acid at 185 °C and then were annealed at 400 °C for times t from 6 to 240 min in wet flowing oxygen. For the Z-cut crystals, fit of the SIMS measured H profiles by expressions obtained from the diffusion equation for diffusion from a finite layer gave a substitutional H diffusivity of DZs=5.0±0.3×10−12 cm2/s and an interstitial H diffusivity of DZi=1.4±0.1×10−11 cm2/s. The wet flowing oxygen acts as a constant source of interstitial H at the surface with the diffusivity DZi and gives an integrated H concentration due to the flowing wet oxygen which increases as (square root of)t. The Li diffusivity was DLiZ=4.8±0.2×10−12 cm2/s which is nearly equal to DZs. For X-cut crystals, the substitutional H diffusivity was DXs=3.4±0.2×10−12 cm2/s and the interstitial diffusivity was DXi=1.3±0.2×10−11 cm2/s. The ne profiles were evaluated by means of optical prism-coupling measurements and numerical simulations. In both cases of crystal orientation, the effective index diffusivity is nearly equal to the diffusivity of substitutional H. Furthermore, there is an excellent linear relationship between the ne profile and the corresponding substitutional H distribution. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358738
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of oxygen incorporation in semi-insulating (AlxGa1−x)yIn1−yP (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1046-1048 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oxygen-doped, semi-insulating layers of (AlxGa1−x)yIn1−yP with x=0.4 were grown on GaAs using organometallic vapor phase epitaxy (OMVPE). Secondary-ion mass spectrometry measurements show that the oxygen incorporation is proportional to the flow rate of O2 into the OMVPE reactor. Two-terminal metal-insulator-semiconductor devices were fabricated and used to evaluate the electrical characteristics of the (AlxGa1−x)yIn1−yP. Traps into the (AlxGa1−x)yIn1−yP bulk behave like DX centers, and are believed to be related to residual Si contamination. Increasing the oxygen concentration in the (AlxGa1−x)yIn1−yP layer decreases the trap concentration by the formation of oxygen complexes with the Si atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350396
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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Ultrafast optical characterization of carrier capture times in InxGa1−xN multiple quantum wells (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 109-111 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Subpicosecond wavelength-degenerate differential transmission optical spectroscopy was used to characterize the electron capture time in a 10-period InxGa1−xN multiple-quantum-well (MQW) structure. Photoluminescence and photoluminescence excitation spectroscopies demonstrated enhanced MQW emission for injection within ±50 meV of the barrier energy. Time-resolved differential transmission measurements for excitation in this region reveal efficient electron capture in the quantum wells with a time constant between 310 and 540 fs. A slower exponential relaxation, with strongly wavelength-dependent subnanosecond decay constants, is also observed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126893
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  • 9
    Electronic Resource
    Electronic Resource
    Linear optical properties of a heavily Mg-doped Al0.09Ga0.91N epitaxial layer (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3188-3190 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped (∼5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124102
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  • 10
    Electronic Resource
    Electronic Resource
    Low interface trap density for remote plasma deposited SiO2 on n-type GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1850-1852 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal-oxide-semiconductor capacitors were prepared with remote plasma-enhanced chemical vapor deposition of SiO2 at ∼300 °C on an n-type GaN epitaxial layer grown by atmospheric pressure metalorganic chemical-vapor deposition on a sapphire substrate. No hysteresis was observed in the high-frequency capacitance-voltage (C−V) measurements, and the measured C−V curve agreed with the C−V behavior calculated for an ideal oxide with the same flat-band voltage as the measured C–V curve. The absence of hysteresis and stretchout in the measured C–V curve and the increase of capacitance with incident ultraviolet light while in deep depletion suggest a low concentration of interface traps. These results demonstrate previous predictions of the absence of Fermi-level stabilization at the interface for the ionic crystal GaN. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116034
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