Polar optical phonon modes of a wurtzite ZnO/MgZnO multi-shell spherical quantum dot

2011 ◽  
Author(s):  
Li Zhang
Keyword(s):  
Quantum Dot ◽  
Optical Phonon ◽  
Polar Optical Phonon ◽  
Phonon Modes ◽  
Spherical Quantum Dot

scholarly journals Crystallographic Orientation Effect On Hole Polar Optical Phonon Scattering Rates in Thin Gaas/Alxga1-Xas Quantum Wells

2019 ◽  
Author(s):  
Mohamed Boumaza
Keyword(s):  
Quantum Wells ◽  
Optical Phonon ◽  
Phonon Scattering ◽  
Strain Effect ◽  
Polar Optical Phonon ◽  
Phonon Modes ◽  
Bulk Gaas ◽  
Hole Energy ◽  
Optical Phonon Scattering ◽  
Scattering Rates

We report on hole polar optical phonon scattering processes in thin GaAs/AlxGa1-xAs quantum wells grown in various crystallographic directions, such as [001], [110]. Using the dielectric continuum model we focus on how the different scattering processes of holes with interface phonon modes depend on the initial hole energy. In our work, we use the Luttinger-Kohn (LK) 6×6 k.p Hamiltonian with the envelope function approximation, from which we compute numerically the electronic structure of holes for a thin quantum well sustaining only one bound state for each type of hole. Due to mixing between the heavy, light, and split off bands, hole subbands exhibit strong nonparabolicity and important warping that have their word to say on physical properties. Detailed and extensive calculations that the rates for intra-subband scattering processes differ significantly from those of bulk GaAs because of quantization and reduced dimensionality. Moreover, the study of scattering as a function of hole energy shows that the trend of the scattering rates is governed mostly by i) overlap integrals and ii) the density of the final states to which the hole scatters. The influence of warping, in the hole energy dispersion, on the phonon scattering rates is also explored and found to be important when the initial hole energy is high. Our calculations show evidence of strong anisotropy in the scattering rates especially for processes involving the heavy hole subband, which anisotropy is in fact quite important and far from being negligible. However, strain effect can reduce scattering rates.

Polar optical phonon states and their degenerative behaviors of wurtziteZnO/MgZnOcoupling quantum dots

2014 ◽  
Vol 28 (11) ◽  
pp. 1430005 ◽  
Author(s):  
Li Zhang ◽  
J. J. Shi
Keyword(s):  
Quantum Dots ◽  
Optical Phonon ◽  
Quantum Systems ◽  
Quantum Structures ◽  
Polar Optical Phonon ◽  
Confined Systems ◽  
Phonon Modes ◽  
Electron Phonon Coupling ◽  
Low Dimensional ◽  
Theoretical Results

Analytical polar optical phonon states in a wurtzite ZnO -based cylindrical coupling quantum dots (CQDs) with arbitrary number of quantum dots (QDs) are deduced and analyzed. It is found that there are four types of polar mixing optical phonon modes, i.e., the z-IO/ρ-QC modes, the z-PR/ρ-IO modes, the z-QC/ρ-QC modes and the z-HS/ρ-IO modes coexisting in the ZnO -based CQDs. Within the framework of the macroscopic dielectric continuum model, the dispersive equations are derived by using the transferring matrix method. And the Fröhlich electron–phonon interaction Hamiltonians are obtained via a standard procedure of field quantization. The relationships between the present ZnO -based CQDs and the ZnO -based quantum wells (QWs) or the nanowires (NWs) are analyzed, and the general features of phonon modes in ZnO -based low-dimensional quantum structures are concluded and discussed. Under certain conditions, the present theoretical results in wurtzite ZnO -based CQDs can be naturally degenerate into those in wurtzite ZnO -based single or double QDs, wurtzite NWs and QWs and even into cubic quantum confined structures. This just embodies the intrinsic consistency of phonon mode theories in low-dimensional confined systems with different confined dimensions. Due to the ternary mixing effect of MgxZn1-xO crystal, the dielectric functions of MgxZn1-xO crystals are quite complicated, and the phonon modes in ZnO -based quantum structures have both the features of phonon modes in anisotropic wurtzite confined systems and isotropic rock-salt crystal quantum systems. The characteristics of electron–phonon coupling strength in ZnO -based quantum systems are summarized. Very strong polaronic effect could be prognosticated and anticipated in ZnO -based low-dimensional quantum structures because of their quite large electron–phonon coupling constants. The theoretical results and conclusions described in this paper also can be looked on as a summary of phonon states and their general features in ZnO -based quantum confined systems.

scholarly journals Mapping the Nanoscale Redshift of Optical Phonon Modes in a Strained Quantum Dot System

2019 ◽  
Vol 25 (S2) ◽  
pp. 626-627
Author(s):  
Chaitanya Gadre ◽  
Xingxu Yan ◽  
Toshihiro Aoki ◽  
Sheng-Wei Lee ◽  
Xiaoqing Pan
Keyword(s):  
Quantum Dot ◽  
Optical Phonon ◽  
Phonon Modes
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