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  • 1
    Electronic Resource
    Electronic Resource
    Electron interaction with confined acoustic phonons in cylindrical quantum wires via deformation potential (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2815-2822 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of phonon confinement on electron–acoustic-phonon scattering is studied in cylindrical semiconductor quantum wires. In the macroscopic elastic continuum model, the confined-phonon dispersion relations are obtained for several crystallographic directions with the two cardinal boundary conditions: free-surface and clamped-surface boundary conditions. The scattering rates due to the deformation potential interaction are obtained for these confined phonons and are compared with those of bulk-like phonons for a number of quantum wire materials. The results show that the inclusion of acoustic phonon confinement effects may be crucial for calculating accurate low-energy electron scattering rates in nanostructures. It is also demonstrated that the scattering rates may be significantly influenced by the direction of phonon propagation, especially for low-energy electrons. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates: the directions characterized by small Poisson ratios exhibit large scattering rates. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363199
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  • 2
    Electronic Resource
    Electronic Resource
    A Monte Carlo study of hot electron injection and interface state generation model for silicon metal-oxide-semiconductor field-effect transistors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5087-5094 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper describes a model which can predict the quantity and lateral distribution of hot-electron-induced interface states in Si metal-oxide-semiconductor field-effect transistors (MOSFETs). The results are obtained using an advanced Monte Carlo method, which incorporates two lowest conduction energy bands from pseudopotential calculations, coupled with an interface state generation model. The coupled model simulates transport-induced hot electron emission from Si into SiO2 and the subsequent generation of interface states in MOSFETs operating under realistic high-voltage stress conditions. The calculations explore the sensitivity of the channel electron energy distribution to various Monte Carlo parameters, such as impact ionization coefficients, self-consistent electron-electron interactions, and surface scattering. Within the validity of our treatments of these physical phenomena, it is shown that while the effects of Monte Carlo parameters on the energy distribution can result in uncertainties in the net interface state generation, quantitative studies may be allowed by using scaling principles. The interface state distribution obtained from the model agrees with experimental data from charge pumping measurements. The model also predicts that the interface state generation extends spatially beyond the range which is accessible by the charge pumping measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355752
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  • 3
    Electronic Resource
    Electronic Resource
    Quantized acoustic phonon modes in quantum wires and quantum dots (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4670-4675 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Acoustic phonon modes in isotropic cubic media are derived for a number of quantum-wire and quantum-dot geometries of significant interest in nanoelectronics and optoelectronics. In each case, the mode amplitude is determined by requiring that the mode energy be given by that of the properly quantized phonon. For the case of cylindrical quantum wires and quantum dots with rectangular faces, the Hamiltonians for the deformation potential interactions are derived. These quantized acoustic modes and the associated deformation potential Hamiltonians provide a basis for modeling carrier-acoustic-phonon interactions in a variety of mesoscopic devices. Our new results supplement previous treatments of related piezoelectric effects in cylindrical quantum wires.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357305
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical calculation of longitudinal-optical-phonon lifetime in GaAs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3905-3907 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The anharmonic decay of longitudinal-optical (LO) phonons in zinc-blende semiconductors has been studied. Based on an approach in which the anharmonic crystal potential is estimated using the theory of elasticity, the lifetime of LO phonons via emission of two acoustic phonons is calculated as a function of lattice temperature and phonon wave vector. Application of this model to bulk GaAs shows an excellent agreement with available experimental data. Since the parameters employed in the model can be obtained experimentally, the approach provides a useful tool to investigate LO-phonon lifetimes in semiconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358498
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Optical properties of ultrathin GaAs/AlAs quantum well structures with an electric field (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8675-8681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical study of the optical properties of GaAs/AlAs quantum well structures in the presence of an electric field is presented. In the first part of the article, interband transitions from the valence band to the conduction band are studied near the type-I to type-II transition point. In the second part, the effect of the electric field on intersubband transitions within the conduction band is considered. The band structure is calculated using a second-nearest-neighbor empirical sp3 tight binding method including spin–orbit effects. Interband and intersubband transition energies, optical matrix elements, and absorption coefficients are given as functions of the electric field. It is shown that the optical properties of these structures can be modified significantly with field near the anticrossing point. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362493
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Quantized vibrational modes of nanospheres and nanotubes in the elastic continuum model (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5107-5111 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of nanoscale spheres and tubes are of recent interest due to the discovery of the fullerene molecule and the carbon nanotube. These carbon structures can be modeled as nanoscale spherical or cylindrical shells. In this article, these nanostructures are treated in the thin shell approximation with the elastic properties taken to be those of the graphene sheet. A quantization prescription is applied to the classical elastic modes to facilitate the first calculations of the quantum-mechanical normalizations of selected modes. These modes are shown to be amenable to the study of electron-phonon interactions. Indeed, electron-phonon interaction Hamiltonians are derived. Moreover, it is shown for such a tube of finite length that the electron-phonon interaction strength depends on the axial position. As a special case it is shown that the dispersion relation for the clamped tube depends on the length of the tube. In this article we consider both the vibrational frequencies and the mode quantization for both spherical shell and the nanotube using realistic material parameters. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356429
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  • 9
    Electronic Resource
    Electronic Resource
    Advances in reflectometric density profile measurements on the DIII-D tokamaka) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1229-1232 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Significant improvements have been achieved in the accuracy and reliability of broadband frequency-swept (FM) reflectometer measurements on DIII-D. This has been achieved through several improvements, the most important of which has been the application of digital complex demodulation (CDM) analysis software, which can extract signal phase with subfringe accuracy. Using this new analysis technique, results from the broadband FM system look very promising: reflectometer measurements show excellent agreement with Thomson profiles in Ohmic and H-mode plasmas, and good agreement with Thomson data in L-mode. Clear resolution of the steep edge density profile in H-mode plasmas, where very small phase shifts are involved, confirm the accuracy of the system calibration and performance. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146012
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  • 10
    Electronic Resource
    Electronic Resource
    Advances in reflectometric density profile measurements on the DIII-D tokamak (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 851-851 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Significant improvements have been achieved in the accuracy and reliability of broadband frequency-swept (FM) reflectometer measurements on DIII-D. This has been achieved through several improvements, the most important of which has been the application of digital complex demodulation (CDM) analysis software, which can extract signal phase with subfringe accuracy. Using this new analysis technique, results from the broadband FM system look very promising: reflectometer measurements show excellent agreement with Thomson profiles in Ohmic and H-mode plasmas, and good agreement with Thomson data in L-mode. Clear resolution of the steep edge density profile in H-mode plasmas, where very small phase shifts are involved, confirm the accuracy of the system calibration and performance. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146248
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