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  • 1
    Electronic Resource
    Electronic Resource
    Dynamic behavior of photocarriers in a GaAs metal-semiconductor-metal photodetector with sub-half-micron electrode pattern (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 567-569 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simulation results of the temporal evolution of photocurrent in an interdigitated GaAs metal-semiconductor-metal photodetector are presented. The dependence of response time on the distance between fingers (0.1 and 0.25 μm) is investigated. The solutions of the time-dependent Schrödinger equation and ensemble Monte Carlo calculations are employed. For a device with 0.1 μm finger spacing, the response time of an intrinsic detector is less than 2 ps, with hole current decay being the major limiting factor. The role of parasitics is shown to significantly increase the simulated response time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100933
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric response functions of heavily doped zincblende semiconductors with finite particle lifetime (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4139-4147 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric response functions in the valence bands and in the conduction band of heavily doped zincblende semiconductors have been evaluated using the self-consistent field method and incorporating the finite lifetime of particles in the relaxation time approximation. Scattering rates of injected electrons are calculated with the Born approximation in the dielectric response function formalism at finite temperature. The finite particle lifetime introduces significant modifications to the spectral density function {Im[−1/ε(q,ω)]} at small q, where collective excitations (i.e., coupled phonon-plasmon modes) are heavily damped due to collisions. However, these modifications are small at large q. At the same time, the scattering rates of injected electrons are strongly affected by the temperature dependence of these effects, which are particularly significant for p-type semiconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352222
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  • 3
    Electronic Resource
    Electronic Resource
    Strain effects on optical gain in wurtzite GaN (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 386-391 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strain effects on optical gain in hexagonal bulk GaN are calculated and explained in terms of the change in the effective hexagonal crystal field component. Qualitatively, even unstrained wurtzite structures correspond to cubic crystals with a proper biaxial stress applied. Such biaxial stress results in effective tensile deformation along the c axis ([111] direction in cubic crystals) and compressive strain in the perpendicular plane. Therefore, the light mode with a polarization vector parallel to the c axis is suppressed, while the mode with a perpendicular polarization is enhanced in wurtzite structures. Thus, compared to cubic structures with similar material parameters, a strong optical anisotropy of wurtzites results in enhanced gain for certain light polarizations, which make wurtzite structures superior for lower-threshold lasing. These qualitative arguments are illustrated by numerical calculations of optical gain in biaxially strained wurtzite GaN, based on a 6×6 envelope-function Hamiltonian. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365824
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  • 4
    Electronic Resource
    Electronic Resource
    Transient ballistic transport in GaN (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2901-2903 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Monte Carlo simulations have been used to study the spatial scales of electron ballistic transport in GaN. The large optical phonon energy (92 meV) and the large intervalley energy separation between the Γ and satellite conduction band valleys (≥1.5 eV) suggest an increasing role for ballistic electron effects in GaN, especially when compared with most III–V semiconductors such as GaAs. However, the concomitant high polar optical phonon scattering rate in GaN tends to diminish the desirable electron transport properties. The relationships between these two factors have been studied for the range of electric fields up to 140 kV/cm and lattice temperatures between 300 and 600 K. We demonstrate that in most cases electrons in GaN lose their directed average velocity over distances of only 100−200 Å, and ballistic transport occurs only over such short distances. The main cause for the small spatial scales of ballistic transport in GaN is the strong electron–optical phonon coupling which results in rapid relaxation of the directed electron velocity.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363952
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical study of electron transport in gallium nitride (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2834-2836 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper describes characteristic electron transport properties for GaN in bulk and quantum well structures. First, ensemble Monte Carlo calculations of steady-state electron drift velocity in bulk GaN are presented as a function of applied electric field for different lattice temperatures. At 300 K, the calculated peak steady-state drift velocity is 2.8×107 cm/s and the threshold field is 160 kV/cm. It is found that the peak steady-state electron drift velocity decreases only slightly by about 20% as the temperature increases from 300 to 600 K while the threshold field increases slightly by about 20%. Therefore, in addition to its high temperature stability, GaN has a low temperature coefficient making it ideal for high temperature applications. For electron transport in heterostructures, quantum mechanical calculations of the electron capture rate in GaN-based quantum wells as a function of well thickness are also presented. An oscillatory behavior of the electron capture rate as a function of quantum well thickness is observed. It is found that the electron capture time oscillates between 2 and 30 ps, which is about an order of magnitude greater than capture times in GaAs quantum wells. The amplitude of oscillations decreased as the well thickness increased. These results suggest that electron transport and carrier collection in GaN are efficient processes for improved electronic and optoelectronic devices. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358696
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  • 6
    Electronic Resource
    Electronic Resource
    Construction of higher-moment terms in the hydrodynamic electron-transport model (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6197-6207 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A critical step in the development of all hydrodynamic transport models (HTMs), derived from moments of the Boltzmann transport equation, is the introduction of accurate closure relations to terminate the resulting infinite set of macroscopic equations. In general, there are a number of resulting integral terms that are highly dependent on the form of the true electron distribution function. The so-called heat flux term is one very important higher-moment term that requires attention. Methods for the accurate construction of an improved heat-flux model are presented. In this construction, a higher-moments approach is combined with a unique definition of electron temperature (i.e., based upon an ansatz distribution) to investigate the effects of conduction-band nonparabolicity and distributional asymmetry. The Monte Carlo method has been used to evaluate the resulting model closures and to study microscopic electron dynamics. These investigations have identified an important relationship between a particular symmetric (i.e., thermal) component of the electron distribution function and the heat flow vector. This knowledge is important because all the parameters in the HTM must be closed (i.e., related to each other through a common set of system variables) before the technique can be accurately applied to the study of electron transport in semiconductor devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355189
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of doping variations on electron transport in GaAs n+-n-n+ structures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5695-5701 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron transport properties in GaAs n+-n-n+ structures with varying doping profiles (in the direction of electron transport) are investigated using self-consistent ensemble Monte Carlo simulations. In particular, we study the effects of ramp doping [i.e., linearly increasing (ramp-up) or decreasing (ramp-down) doping density within the n region] and spike doping (i.e., introducing one or more n+ spikes in the n region) on electron transport to assess differences, advantages, and potential applications of these doping profiles on device performance. Underlying physical mechanisms for electron transport in these structures are analyzed. Simulation results reveal that overall electron transport can be improved significantly by employing ramp-up (rather than ramp-down) doping and multispike (instead of single-spike) doping schemes. Potential advantages of variable doping in field-effect transistor applications include enhanced current drive capability, reduced source resistance, and improved breakdown characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351920
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of DX centers and surface states on δ-doped high-electron-mobility transistor performance (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4123-4128 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The roles of DX centers and surface states associated with the n-AlGaAs layer of δ-doped AlGaAs/GaAs high-electron-mobility transistors have been investigated by employing a two-dimensional, self-consistent ensemble Monte Carlo simulation. It is found that both DX centers and surface states degrade device performance, particularly as gate-to-source voltage increases. This degradation is manifested largely through reduced channel electron concentration, increased intervalley scattering, and enhanced real-space transfer. Of the two defect states, DX centers have more detrimental influence on drain current and transconductance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348425
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  • 9
    Electronic Resource
    Electronic Resource
    Bipolar transistor with ion implanted, rapid thermal annealed base and semi-insulating polycrystalline silicon emitter (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2831-2838 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The purpose of this work was to investigate the use of ion implantation combined with rapid thermal annealing for the base and semi-insulating polycrystalline silicon (SIPOS) for the emitter of a bipolar transistor. The microstructure of the SIPOS/Si interface after rapid thermal annealing conditions and its influence on the electrical performance of the device was studied. The SIPOS/Si interface was found to be more stable than the polysilicon/Si interface after similar processing conditions, and a thin interfacial oxide layer was observed to inhibit epitaxial alignment at the interface. Lower emitter series resistances were obtained for devices where epitaxial alignment occurred at the interface, however, no quantitative correlation was observed between the microstructure of the interface and the current gain of the transistor. Bipolar transistors with enhanced current gain/base resistance ratios were fabricated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340986
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  • 10
    Electronic Resource
    Electronic Resource
    Theory of the velocity-field relation in AlGaAs (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5004-5008 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present ensemble Monte Carlo calculations of the steady-state electron drift velocity as a function of applied electric field in Al0.32 Ga0.68 As. The effect of various material parameters on the calculated velocity is assessed by varying each parameter independently by ±20%. It is found that both the optical phonon energy and intervalley separation energy alter the peak electron velocity greatly. Variations in the dielectric constants and central valley effective mass have little effect upon the peak drift velocity, but act to alter the threshold electric field. It is further found that the threshold electric field is greater in Al0.32Ga0.68As than in GaAs even though the central-to-satellite valley separation energy is less in AlGaAs. The combined effects of a greater central valley effective mass and a larger phonon energy in AlGaAs result in a greater threshold field. Finally, we present sets of material parameters useful in Monte Carlo models for both GaAs and AlGaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340446
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