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Michael A Stroscio - One of the best experts on this subject based on the ideXlab platform.
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Interface Optical Phonon modes in wurtzite quantum heterostructures
2010 14th International Workshop on Computational Electronics, 2010Co-Authors: Sicheng Liao, Mitra Dutta, Michael A StroscioAbstract:This paper formulated the interface Optical Phonon modes for two particular asymmetrical heterostructures: SiC/GaN/Vacuum and AIN/GaN/Vacuum. The interface Optical Phonon potentials and dispersion relations are determined for these structures. Using these results, the carrier-interface-Phonon interaction Hamiltonian is formulated.
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Surface-Optical Phonon assisted transitions in quantum dots
Journal of Applied Physics, 2004Co-Authors: Chen Chen, Mitra Dutta, Michael A StroscioAbstract:The Frohlich interaction between electrons and surface-Optical Phonons is studied by using the dielectric continuum model. First, the eigenfrequencies of the surface Phonons are calculated. A result for the normalized displacement of the Phonon is obtained and a more accurate electron-surface Phonon Frohlich interaction Hamiltonian is calculated. The surface-Optical-Phonon-assisted scattering rate of an electron in free-standing GaN quantum dots is calculated with natural linewidth broadening. Finally, illustrative examples of surface-Optical-Phonon-assisted scattering rates are calculated to clarify the potential importance of SO-Phonon-assisted transitions in potential applications of quantum dots.
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Electron–Optical-Phonon scattering in wurtzite crystals
Physical Review B, 1997Co-Authors: B. C. Lee, Mitra Dutta, Ki Wook Kim, Michael A StroscioAbstract:We present Fr\"ohlich-like electron--Optical-Phonon interaction Hamiltonian for wurtzite crystals in the long-wavelength limit based on the macroscopic dielectric continuum model and the uniaxial model. In general, the Optical-Phonon branches support mixed longitudinal and transverse modes due to the anisotropy. We calculate electron scattering rate due to the Optical Phonons in the bulk wurtzite GaN and demonstrate that the scattering rate due to transverselike Phonon processes can be strongly enhanced over a range of angles with respect to the $c$ axis. For the case of longitudinal-like modes, the anisotropy is small and the result is almost the same as that obtained with the cubic Fr\"ohlich Hamiltonian.
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Real-space transfer of photoexcited electrons in type-II superlattices via Optical-Phonon emission
Physics and Simulation of Optoelectronic Devices II, 1994Co-Authors: M. U. Erdogan, Michael A Stroscio, Ki Wook Kim, V. Sankaran, Gerald J IafrateAbstract:The (Gamma) -X scattering rate of electrons in type-II superlattices by Optical-Phonon emission is calculated. The tight binding method for electronic band structure and the dielectric continuum model for Phonons are used. The relative strength of scattering due to different Phonon modes is examined for varying superlattice dimensions. The scattering rate is highest when the energy separation between the (Gamma) and X levels is smallest, and decreases quickly as the separation increases. It is found that the strongest scattering rate is due to the emission of AlAs confined modes. Changing of parity with layer thickness and its effect on scattering are discussed.
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transition from longitudinal Optical Phonon scattering to surface Optical Phonon scattering in polar semiconductor superlattices
Applied Physics Letters, 1991Co-Authors: Michael A Stroscio, Gerald J Iafrate, Michael A. Littlejohn, Herbert Goronkin, George N. MaracasAbstract:Dielectric continuum models of Optical‐Phonon modes predict an enhancement in the strength of the surface‐Optical (SO) modes in double‐barrier heterostructures as the heterojunction‐to‐heterojunction separation is reduced. There is currently no consensus on the nature of the electron‐SO‐Phonon coupling interaction. In this work, the ratio of electron scattering by the SO‐Phonon modes to that by the confined longitudinal‐Optical (LO) Phonon modes is calculated for a GaAs/AlAs short‐period superlattice based on the assumption that the electron‐SO‐Phonon interaction may be described by a scalar potential. The scaling of the ratio of electron‐SO‐Phonon scattering to electron‐LO‐Phonon scattering as a function of the superlattice period provides a sensitive test of the appropriateness of the scalar‐potential model.
Ki Wook Kim - One of the best experts on this subject based on the ideXlab platform.
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Electron–Optical-Phonon scattering in wurtzite crystals
Physical Review B, 1997Co-Authors: B. C. Lee, Mitra Dutta, Ki Wook Kim, Michael A StroscioAbstract:We present Fr\"ohlich-like electron--Optical-Phonon interaction Hamiltonian for wurtzite crystals in the long-wavelength limit based on the macroscopic dielectric continuum model and the uniaxial model. In general, the Optical-Phonon branches support mixed longitudinal and transverse modes due to the anisotropy. We calculate electron scattering rate due to the Optical Phonons in the bulk wurtzite GaN and demonstrate that the scattering rate due to transverselike Phonon processes can be strongly enhanced over a range of angles with respect to the $c$ axis. For the case of longitudinal-like modes, the anisotropy is small and the result is almost the same as that obtained with the cubic Fr\"ohlich Hamiltonian.
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Real-space transfer of photoexcited electrons in type-II superlattices via Optical-Phonon emission
Physics and Simulation of Optoelectronic Devices II, 1994Co-Authors: M. U. Erdogan, Michael A Stroscio, Ki Wook Kim, V. Sankaran, Gerald J IafrateAbstract:The (Gamma) -X scattering rate of electrons in type-II superlattices by Optical-Phonon emission is calculated. The tight binding method for electronic band structure and the dielectric continuum model for Phonons are used. The relative strength of scattering due to different Phonon modes is examined for varying superlattice dimensions. The scattering rate is highest when the energy separation between the (Gamma) and X levels is smallest, and decreases quickly as the separation increases. It is found that the strongest scattering rate is due to the emission of AlAs confined modes. Changing of parity with layer thickness and its effect on scattering are discussed.
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Transition from longitudinal‐Optical Phonon scattering to surface‐Optical Phonon scattering in polar semiconductor superlattices
Applied Physics Letters, 1991Co-Authors: Michael A Stroscio, Gerald J Iafrate, Michael A. Littlejohn, Herbert Goronkin, Ki Wook Kim, George N. MaracasAbstract:Dielectric continuum models of Optical‐Phonon modes predict an enhancement in the strength of the surface‐Optical (SO) modes in double‐barrier heterostructures as the heterojunction‐to‐heterojunction separation is reduced. There is currently no consensus on the nature of the electron‐SO‐Phonon coupling interaction. In this work, the ratio of electron scattering by the SO‐Phonon modes to that by the confined longitudinal‐Optical (LO) Phonon modes is calculated for a GaAs/AlAs short‐period superlattice based on the assumption that the electron‐SO‐Phonon interaction may be described by a scalar potential. The scaling of the ratio of electron‐SO‐Phonon scattering to electron‐LO‐Phonon scattering as a function of the superlattice period provides a sensitive test of the appropriateness of the scalar‐potential model.
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Theory of Optical-Phonon interactions in a rectangular quantum wire
Physical Concepts of Materials for Novel Optoelectronic Device Applications II: Device Physics and Applications, 1991Co-Authors: Michael A Stroscio, Ki Wook Kim, Michael A. LittlejohnAbstract:The Hamiltonian describing the iteraction of both confined longitudinal-Optical and surface-Optical photons with charge carriers is derived from the macroscopic dielectric continuum model for the case of a rectangular quantum wire where photon confinement occurs in two of the three spatial dimensions. The full interaction Hamiltonian is used to calculate the total scattering rate for electron-Optical-Phonon scattering of electrons traversing a GaAs square quantum wire. The results demonstrate that the interaction by the surface-Optical Phonon modes is very strong and may dominate over other scattering processes, especially with dimensions of about 100 A or less. A considerable decrease in the total scattering rate for Optical Phonons as a result of simple reduction in dimensionality is not observed in this study.
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Electron‐Optical‐Phonon scattering rates in a rectangular semiconductor quantum wire
Journal of Applied Physics, 1991Co-Authors: Ki Wook Kim, Michael A Stroscio, A. R. Bhatt, R. Mickevicius, Vladimir MitinAbstract:One‐dimensional electron‐Optical‐Phonon interaction Hamiltonians in a rectangular quantum wire consisting of diatomic polar semiconductors are derived under the macroscopic dielectric continuum model. The scattering rates calculated in a GaAs square quantum wire show that when the quantum wire is free‐standing in vacuum, the interaction by the surface‐Optical Phonon modes is very strong and may dominate over other scattering processes, especially with dimensions of about 100 A or less. When the wire is embedded in a polar semiconductor (AlAs to be specific), the scattering rates by the surface‐Optical Phonon modes become generally smaller, but yet comparable to those by the confined longitudinal‐Optical modes as the wire dimension shrinks. A considerable decrease in the total scattering rate for Optical Phonons as a result of simple reduction in dimensionality is not observed in this study.
George N. Maracas - One of the best experts on this subject based on the ideXlab platform.
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transition from longitudinal Optical Phonon scattering to surface Optical Phonon scattering in polar semiconductor superlattices
Applied Physics Letters, 1991Co-Authors: Michael A Stroscio, Gerald J Iafrate, Michael A. Littlejohn, Herbert Goronkin, George N. MaracasAbstract:Dielectric continuum models of Optical‐Phonon modes predict an enhancement in the strength of the surface‐Optical (SO) modes in double‐barrier heterostructures as the heterojunction‐to‐heterojunction separation is reduced. There is currently no consensus on the nature of the electron‐SO‐Phonon coupling interaction. In this work, the ratio of electron scattering by the SO‐Phonon modes to that by the confined longitudinal‐Optical (LO) Phonon modes is calculated for a GaAs/AlAs short‐period superlattice based on the assumption that the electron‐SO‐Phonon interaction may be described by a scalar potential. The scaling of the ratio of electron‐SO‐Phonon scattering to electron‐LO‐Phonon scattering as a function of the superlattice period provides a sensitive test of the appropriateness of the scalar‐potential model.
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Transition from longitudinal‐Optical Phonon scattering to surface‐Optical Phonon scattering in polar semiconductor superlattices
Applied Physics Letters, 1991Co-Authors: Michael A Stroscio, Gerald J Iafrate, Michael A. Littlejohn, Herbert Goronkin, Ki Wook Kim, George N. MaracasAbstract:Dielectric continuum models of Optical‐Phonon modes predict an enhancement in the strength of the surface‐Optical (SO) modes in double‐barrier heterostructures as the heterojunction‐to‐heterojunction separation is reduced. There is currently no consensus on the nature of the electron‐SO‐Phonon coupling interaction. In this work, the ratio of electron scattering by the SO‐Phonon modes to that by the confined longitudinal‐Optical (LO) Phonon modes is calculated for a GaAs/AlAs short‐period superlattice based on the assumption that the electron‐SO‐Phonon interaction may be described by a scalar potential. The scaling of the ratio of electron‐SO‐Phonon scattering to electron‐LO‐Phonon scattering as a function of the superlattice period provides a sensitive test of the appropriateness of the scalar‐potential model.
Wen-feng Hsieh - One of the best experts on this subject based on the ideXlab platform.
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reducing exciton longitudinal Optical Phonon interaction with shrinking zno quantum dots
Applied Physics Letters, 2007Co-Authors: Wen-feng HsiehAbstract:The exciton-longitudinal-Optical-Phonon (LO-Phonon) interaction was observed to decrease with reducing ZnO particle size to its exciton Bohr radius (aB). The unapparent LO-Phonon replicas of free exciton (FX) emission and the smaller FX energy difference between 13 and 300K reveal decreasing weighting of exciton-LO Phonon coupling strength. The diminished Frohlich interaction mainly results from the reducing aB with size due to the quantum confinement effect that makes the exciton less polar.
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Acoustic and Optical Phonon assisted formation of biexcitons
Applied Physics Letters, 2007Co-Authors: Ching-ju Pan, Kuo-feng Lin, Wen-feng HsiehAbstract:Efficient exciton relaxation is required for bounding two cooled excitons to form biexciton. Acoustic and Optical Phonon scatterings playing key roles in exciton relaxation are responsible for formation of biexcitons at various temperatures. Using ZnO powders, the authors observed a sublinear dependence on excitation power at low temperature, in which the relaxation process involves only emission of acoustic Phonons due to the excitons having kinetic energy lower than those of the Optical Phonons. However, the exponent comes near theoretical value of 2 for participation of Optical Phonons when the exciton kinetic energy approaches to the energy of the lowest Optical Phonon.
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band gap engineering and spatial confinement of Optical Phonon in zno quantum dots
Applied Physics Letters, 2006Co-Authors: Kuo-feng Lin, Hsin Ming Cheng, Hsu Cheng Hsu, Wen-feng HsiehAbstract:Both band gap engineering and spatial confinement of Optical Phonon were observed depending upon the size of ZnO quantum dots at room temperature. Size-dependent blueshifts of photoluminescence and absorption spectra reveal the quantum confinement effect. The measured Raman spectral shift and asymmetry for the E2(high) mode caused by localization of Optical Phonons agree well with that calculated by using the modified spatial correlation model.
Kong-thon Tsen - One of the best experts on this subject based on the ideXlab platform.
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subpicosecond time resolved raman studies of electron longitudinal Optical Phonon interactions in inn
Applied Physics Letters, 2007Co-Authors: Kong-thon Tsen, D K Ferry, Juliann G Kiang, Hai Lu, W J SchaffAbstract:Electron–longitudinal Optical Phonon scattering rate in InN has been directly measured by subpicosecond time-resolved Raman spectroscopy. The experimental results show that for a thick layer of InN grown on GaN, the average total electron–longitudinal Optical Phonon scattering rate is (5.1±1.0)×1013s−1. This enormous electron–longitudinal Optical Phonon scattering rate, which is comparable to that observed in GaN, has been attributed to the extremely polar nature of InN.
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coherent longitudinal Optical Phonon and plasmon coupling in the near surface region of inn
Applied Physics Letters, 2004Co-Authors: Yuming Chang, Kong-thon Tsen, Chihmin Chuang, Chihta Chia, H Lu, W J SchaffAbstract:Coherent Phonon spectroscopy of a high-quality InN epitaxial layer is carried out using time-resolved second-harmonic generation. A coherent longitudinal Optical Phonon and plasmon coupling mode only at 447cm−1 can be resolved in the spectrum. Its frequency shows no dependence on the photoinjected carrier density up to 1.5×1019cm−3. This phenomenon is attributed to the hybridization of a coherent A1(LO) Phonon with the intrinsic cold plasma accumulated in the near-surface region of InN, where the plasma density could reach on the order of 1020cm−3, much higher than the bulk carrier concentration 1×1018cm−3 determined by Hall effect measurement.
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non equilibrium electron distributions and electron longitudinal Optical Phonon scattering rates in wurtzite gan
Journal of Electronic Materials, 1998Co-Authors: Kong-thon Tsen, D K Ferry, A Botchkarev, B Sverdlov, A Salvador, Hadis MorkoçAbstract:Non-equilibrium electron distributions and electron-longitudinal Optical Phonon scattering rates in wurtzite GaN have been studied by subpicosecond time-resolved Raman spectroscopy. Our experimental results show that for electron densities n≥5×1017cm−3, the non-equilibrium electron distributions in wurtzite GaN can be very well described by Fermi-Dirac distribution functions with the effective electron temperature much higher than the lattice temperature. In addition, we find that the total electron-longitudinal Optical Phonon scattering rate in GaN is about one order of magnitude larger than that in GaAs. We attribute this enormous increase in the electron-longitudinal Optical Phonon scattering rate to the much larger ionicity in GaN.
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direct measurements of electron longitudinal Optical Phonon scattering rates in wurtzite gan
Applied Physics Letters, 1997Co-Authors: Kong-thon Tsen, D K Ferry, A Botchkarev, B Sverdlov, A Salvador, Hadis MorkoçAbstract:Electron-longitudinal Optical Phonon scattering rates in wurtzite GaN have been directly measured by subpicosecond time-resolved Raman spectroscopy. We find that the total electron-longitudinal Optical Phonon scattering rate in GaN is about one order of magnitude larger than that in GaAs. We attribute this enormous increase in the electron-longitudinal Optical Phonon scattering rate to the much larger ionicity in GaN.Electron-longitudinal Optical Phonon scattering rates in wurtzite GaN have been directly measured by subpicosecond time-resolved Raman spectroscopy. We find that the total electron-longitudinal Optical Phonon scattering rate in GaN is about one order of magnitude larger than that in GaAs. We attribute this enormous increase in the electron-longitudinal Optical Phonon scattering rate to the much larger ionicity in GaN.
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Direct measurements of electron-longitudinal Optical Phonon scattering rates in wurtzite GaN
Applied Physics Letters, 1997Co-Authors: Kong-thon Tsen, D K Ferry, A Botchkarev, B Sverdlov, A Salvador, Hadis MorkoçAbstract:Electron-longitudinal Optical Phonon scattering rates in wurtzite GaN have been directly measured by subpicosecond time-resolved Raman spectroscopy. We find that the total electron-longitudinal Optical Phonon scattering rate in GaN is about one order of magnitude larger than that in GaAs. We attribute this enormous increase in the electron-longitudinal Optical Phonon scattering rate to the much larger ionicity in GaN.