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  • 1
    Electronic Resource
    Electronic Resource
    Modeling the post-burn-in abnormal base current in AlGaAs/GaAs heterojunction bipolar transistors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7348-7352 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The base current of AlGaAs/GaAs heterojunction bipolar transistor subjected to a long burn-in test often exhibits an abnormal characteristic with an ideality factor of about 3, rather than a normal ideality factor between 1 and 2, in the midvoltage range. We develope an analytical model to investigate the physical mechanisms underlying such a characteristic. Consistent with the finding of an experimental work reported recently, our model calculations show that the recombination current in the base has an ideality factor of about 3 in the midvoltage range and that such a current is responsible for the observed abnormal base current in heterojunction bipolar transistor after a long burn-in test. Post-burn-in data measured from two different heterojunction bipolar transistors are also included in support of the model. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361451
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  • 2
    Electronic Resource
    Electronic Resource
    Parametric study of AlAs/GaAs superlattice double-barrier diodes (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 207-209 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum well diodes with barriers formed by thin, short-period binary AlAs/GaAs superlattices were fabricated and found to have very high peak-to-valley current ratios. The effects of varying the AlAs and GaAs layers in the barriers are studied. The peak current density is found to decrease by orders of magnitude for monolayer increases in the AlAs layer thicknesses. Tunneling current peaks due to both resonance levels in the quantum well and resonance levels in the superlattice barriers are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100132
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  • 3
    Electronic Resource
    Electronic Resource
    Base and collector leakage currents of AlGaAs/GaAs heterojunction bipolar transistors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3187-3193 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Base and collector leakage currents are extremely important to AlGaAs/GaAs heterojunction bipolar transistor (HBT) dc characteristics, and a simple model to describe such currents is presented. This study suggests that these currents are originated from the electron and hole leakage through the dielectric-layer (e.g., polyimide, nitride, etc.) interface at the emitter-base and base-collector peripheries, as well as through the n+-subcollector/semi-insulating substrate interface. Five HBTs having similar intrinsic make-ups (i.e., doping concentration and layer thickness) but different extrinsic make-ups (i.e., finger pattern, perimeter, dielectric layer, etc.) are investigated, and with the aid of the model, the possible mechanisms contributing to their leakage behavior identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357502
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  • 4
    Electronic Resource
    Electronic Resource
    Electron density in quantum well diodes (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3126-3130 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent calculation of the electron density and conduction-band edge is presented. The time-independent Schrödinger and Poisson equations are solved simultaneously under a high applied bias for structures with thick, lightly doped spacer layers. It is shown that strongly localized states occur in the well and accumulation regions. These states are capable of trapping a substantial amount of charge, which in turn can drastically change the shape of the band edge, and therefore need to be included in studies of the resonant tunneling problem in which the Coulomb interaction must be accounted for.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344147
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  • 5
    Electronic Resource
    Electronic Resource
    Independence of peak current from emitter spacer layer width in AlGaAs/GaAs resonant tunneling diodes (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5905-5907 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The peak current for the negative differential resistance region of AlGaAs/GaAs resonant tunneling diodes is shown to behave independently of the width of a low-doped emitter spacer layer if an isolated accumulation region forms upstream from the first AlGaAs barrier. The effect of the voltage drop across the emitter spacer layer is shown to be minor. These results appear to confirm that electron transport through these resonant tunneling diodes is a two-step process. In addition, a radial dependency of device performance attributed to molecular beam epitaxy growth conditions is noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347190
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of AlAs/GaAs superlattice barriers using electrical barrier height analysis (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4765-4767 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical barrier height measurements on n+-GaAs–insulator–n-GaAs structures with short-period AlAs/GaAs superlattices forming the insulator show the effective conduction-band discontinuity (ΔEC) of a superlattice barrier (SLB) to be defined by the lowest superlattice energy state. Five structures with different AlAs and GaAs SLB layer thicknesses are investigated. A SLB with GaAs layers greater than 10 monolayers is found to have a ΔEC defined by Γ-valley states in the GaAs layers, while a SLB with GaAs and AlAs layers less than 10 monolayers and with thicker AlAs layers than GaAs layers is found to have a ΔEC defined by X-valley states in the AlAs layers. The SLB with GaAs and AlAs layers less than 10 monolayers and thicker GaAs layers than AlAs layers behaves as a random alloy. Negative differential resistance is observed in the current-voltage characteristic of the sample whose barrier height is defined by Γ-valley states in the GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341194
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  • 7
    Electronic Resource
    Electronic Resource
    Charge-quantization effects on current-voltage characteristics of AlGaAs/GaAs resonant tunneling diodes with spacer layers (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3425-3430 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An inflection has been observed in the current-voltage characteristics of several AlGaAs/GaAs resonant tunneling diodes with spacer layers. We provide evidence linking this inflection, as well as the negative differential resistance, to quasi-bound energy states localized in the charge accumulation well between the emitter spacer layer and the AlGaAs barrier. There are strong indications that this region acts as the injector of electrons through the quantum well region. We propose a model for the electron transport, and show that the singularities in the current are caused by the quantum well state crossing the accumulation layer quasi-bound states as the bias is ramped.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346349
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  • 8
    Electronic Resource
    Electronic Resource
    AlGaAs/GaAs double barrier diodes with high peak-to-valley current ratio (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 121-123 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the largest peak-to-valley current (PVC) ratios to date from AlGaAs/GaAs double barrier (either alloy barrier or superlattice barrier) diodes. PVC ratios as high as 3.6 and 21.7 were obtained from an AlAs/GaAs superlattice barrier structure at 300 and 77 K, respectively. In an alloy barrier structure with x=0.42 (x=0.3), PVC ratios of 3.9 (2.2) and 14.3 (7.0) were observed at 300 and 77 K, respectively. We attribute these excellent results to a "two-step'' spacer layer incorporated in the devices studied which facilitated the growth of high material quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98588
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  • 9
    Electronic Resource
    Electronic Resource
    Percutaneous reposition of dislodged coils in the treatment of a vertebral arteriovenous fistula — with CT follow-up (1991)
    Springer
    Neuroradiology 33 (1991), S. 195-199 
    Details
    ISSN: 1432-1920
    Keywords: Vertebral arteriovenous fistula ; Embolization ; Endovascular occlusion ; Detachable balloon ; CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report a case of vertebral arteriovenous fistula, in which embolization was complicated by migration of two coils and a partially inflated balloon. In order to relieve compression to the spinal cord, the displaced balloon was punctured percutaneously. For both relieving compression to the spinal cord and obliterating the residual fistula, the dislodged coils in the partially thrombosed epidural venous sinus were removed percutaneously and placed in the fistula, and more coils were implanted in the fistula percutaneously through the needle. CT follow-up half a year later showed complete resolution of compression of the spinal cord and complete recovery from myelopathy was clinically apparent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588216
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