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  • 1
    Electronic Resource
    Electronic Resource
    Calculation of the base current components and determination of their relative importance in AlGaAs/GaAs and InAlAs/InGaAs heterojunction bipolar transistors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3328-3334 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The base current density JB is an important parameter in determining the common-emitter current gain β of heterojunction bipolar transistors (HBTs). To develop an analytical β model with which a circuit designer can quickly estimate the current gain in a HBT, it is also important to identify the dominant component of JB so that minimum computations are required. Based on heterojunction device physics, the three components of JB have been calculated, namely, the recombination current density in the base JRB, the recombination current density in the space-charge region JSCR, and the injection current density from the base to the emitter JRE, and have determined their relative importance to JB for abrupt AlGaAs/GaAs and InAlAs/InGaAs HBTs under normal bias conditions. It is found that relative importance of the three current densities depends strongly on the bias condition, strongly on the density of states NtI at the emitter-base heterointerface, but weakly on the density of trapping states NtB in the bulk of the emitter-base space-charge region. Also, JB is relatively insensitive to device makeup such as doping concentration and layer thickness. Depending on NtI and on the bias condition, either JSCR or JRE is the dominant component for AlGaAs/GaAs HBTs and either JSCR or JRB is the dominant component for InAlAs/InGaAs HBTs. Effects of base and heterojunction grading on the present findings are also addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348556
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  • 2
    Electronic Resource
    Electronic Resource
    Reply to "Comments on ‘Effects of using the more accurate intrinsic concentration on bipolar transistor modeling' '' [J. Appl. Phys. 68, 5911 (1990)] (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3975-3976 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This reply addresses the issues raised by Rode and Rosenbaum regarding the bipolar junction transistor model developed in the subject paper [J. Appl. Phys. 68, 5911(1990)]. The error associated with Eq. (4) in the subject paper is discussed and corrected, the value of the space-charge-region recombination time used is specified, and the results are recalculated. It is shown that the error in Eq. (4) does not alter notably the trends of the current gain calculated using the two different intrinsic concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349162
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of using the more accurate intrinsic concentration on bipolar transistor modeling (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5911-5912 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A more accurate intrinsic concentration was suggested recently. Discrepancies between using the conventional and the more accurate intrinsic concentrations on bipolar transistor modeling are assessed in this study. Our calculations show that the conventional intrinsic concentration overestimates the collector and base currents by a factor of 1.5 to 2 but affects less severely the steady-state current gain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346942
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  • 4
    Electronic Resource
    Electronic Resource
    Charge storage in the quasineutral regions of Si homojunction, AlGaAs/GaAs heterojunction, and Si/SiGe heterojunction bipolar transistors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4059-4065 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge storage in the quasineutral regions of a bipolar transistor often limits the switching speed of the device, particularly when the transistor is operated in saturation mode (both emitter-base and base-collector junctions are forward biased), a bias condition which occurs frequently in logic circuits. This paper studies and compares the free-carrier charges stored in the quasineutral regions of the conventional Si homojunction bipolar transistor (Si BJT) and the increasingly important AlGaAs/GaAs and Si/SiGe heterojunction bipolar transistors (HBTs). The diffusion capacitances associated with this stored charge, which are used in the Gummel–Poon bipolar transistor model, are also calculated and discussed. It is shown that the AlGaAs/GaAs HBT has the least carrier accumulation in the quasineutral regions among the three devices due primarily to the relatively large energy band gap of GaAs-related materials. Also, the Si/SiGe HBT is expected to operate at a higher switching speed compared to the Si BJT, because the valence band discontinuity at the Si/SiGe base-collector heteroface impedes the minority-carrier injection from the base into the collector.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350830
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  • 5
    Electronic Resource
    Electronic Resource
    High-level injection in quasi-neutral region of n/p junction devices: Numerical results and empirical model (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1611-1615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ambipolar transport equation is solved numerically to provide the physical insight of high-level free-carrier injection in the quasi-neutral region of n/p junction devices. It is shown that the diffusion current-only approximation used conventionally to model the minority current fails when high-level injection prevails. Our results further suggest that in high-level injection, the drift current is comparable to the diffusion current and that the minority current in the quasi-neutral region is position dependent even if the region is thin. Based on the numerical results, an empirical model is also developed which, while retaining the form of the conventional diffusion current-only model, can accurately describe the current transport in an n/p junction including the effect of high injection. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358915
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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Effects of band-gap narrowing on common-emitter current gain of GaAs homojunction bipolar transistors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 5181-5184 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs homojunction bipolar transistors (GaAs BTs) are attractive because of their manufacturability and high electron mobility. This paper theoretically investigates the band-gap narrowing effects on the common-emitter current gain β of GaAs BTs based on recently reported band-gap-narrowing results for GaAs taking into account interactions between free carriers and dopant ions. It is shown that, benefitting from the band-gap contractions, an n+/ p+ /n GaAs BT can possess good β as well as high cutoff frequency, contrasting with the conventional concept that n+ /p/n doping in a GaAs BT is needed in order to obtain high β. Experimental results reported in literature regarding n+ /p+ /n GaAs BTs are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343147
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  • 9
    Electronic Resource
    Electronic Resource
    Low-temperature p-n junction space-charge-region thickness including the effects of doping-dependent dielectric permittivity (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6369-6372 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper studies the thickness of silicon p-n junction space-charge regions at low temperature including the effects of doping-dependent dielectric permittivity ε(N), which is important for heavily doped semiconductor materials because of the presence of unionized impurity atoms that are subjected to polarization. The treatment is applicable for p-n junctions under all voltages and is not based on the conventional depletion approximation which assumes free carriers are negligible in the space-charge region. Comparison of the present thickness model including ε(N) and the conventional depletion model is included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342072
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  • 10
    Electronic Resource
    Electronic Resource
    Forward-voltage capacitance of heterojunction space-charge regions (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5015-5022 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical treatment is presented for modeling the capacitance of heterojunction space-charge regions under forward voltages. First, the conventional depletion model is reviewed and the inadequacy of the use of such a model at forward voltages is noted. The study then turns to the development of a more accurate model for the thickness and potential barrier of the space-charge region for all voltages. Based on this model and the approximation that the intrinsic level is piecewise linear with respect to position in the space-charge region, an analytical quasistatic capacitance model applicable for forward-biased conditions is derived. The model, however, encounters difficulties at very large forward voltages, and a qualitative treatment is employed there. The comparison of the present capacitance model with measured dependencies and with existing capacitance models is included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340448
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