Growth Evolution of (Zn,Cd)Se Quantum Dots Deduced from Spatially Resolved Structural and Optical Characterization

1999 ◽  
Vol 571 ◽  
Author(s):  
K. Leonard ◽  
D. Hommel ◽  
A. Stockmann ◽  
H. Selke ◽  
J. Seufert ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Wells ◽  
Three Dimensional ◽  
High Energy ◽  
Growth Direction ◽  
Growth Mode ◽  
Gradual Transition ◽  
Mode Transition ◽  
Spatially Resolved ◽  
Composition Fluctuations

ABSTRACTThe growth mode of CdSe layers grown by migration enhanced epitaxy between ZnSe barriers has been investigated. In situ reflection high-energy electron diffraction shows a gradual transition to a three-dimensional growth mode which, however, is not accompanied by a change of the surface lattice constant. High-resolution transmission electron micrographs reveal a strong Cd diffusion, leading to ternary ZnCdSe quantum wells. Furthermore. composition fluctuations perpendicular to the growth direction on a nanometer scale are found already prior to the beginning of the growth mode transition. In the case of heterostructures containing a CdSe layer that has undergone the growth mode transition, micrographs show Cd-rich quantum dots with diameters of around 8 nm and heights of around 1.5 nm within a ternary quantum well. By spatially resolved photoluminescence the emission from single quantum dots could be observed. The polarization dependence of the emission from single dots indicates an asymmetric shape of the dots with certain preferential orientations along the [110] and [110] directions.

A RHEED Study of MBE Growth of ZnSe on GaAs (111) A-(2 × 2)

2003 ◽  
Vol 10 (04) ◽  
pp. 669-675
Author(s):  
F. S. Gard ◽  
J. D. Riley ◽  
R. Leckey ◽  
B. F. Usher
Keyword(s):  
Growth Rate ◽  
Electron Diffraction ◽  
Substrate Temperature ◽  
Three Dimensional ◽  
High Energy ◽  
Growth Mode ◽  
Two Dimensional ◽  
High Energy Electron ◽  
Mbe Growth ◽  
Atomic Flux

ZnSe epilayers have been grown under various Se/Zn atomic flux ratios in the range of 0.22–2.45 at a substrate temperature of 350°C on Zn pre-exposed GaAs (111) A surfaces. Real time reflection high energy electron diffraction (RHEED) observations have shown a transition from a two-dimensional (2D) to a three-dimensional (3D) growth mode. The transition time depends directly upon the growth rate. A detailed discussion is presented to explore the cause of this change in the growth mode.

scholarly journals Магнитная циркулярная поляризация фотолюминесценции экситонов

2018 ◽  
Vol 60 (8) ◽  
pp. 1503
Author(s):  
Е.Л. Ивченко
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Quantum Wells ◽  
Circular Polarization ◽  
Spectral Lines ◽  
Theoretical Studies ◽  
Two Dimensional ◽  
Bulk Semiconductors ◽  
Polarization Of Luminescence ◽  
Composition Fluctuations

AbstractExperimental and theoretical studies of circular polarization of photoluminescence of excitons (MCPL) in semiconductors placed in an external magnetic field are reviewed. The advantage of the MCPL method is its relative simplicity. In particular, it does not require spectral resolution of the Zeeman sublevels of an exciton and may be applied to a wide class of objects having broad photoluminescence spectral lines or bands: in bulk semiconductors with excitons localized on the defects of the crystal lattice and composition fluctuations, in structures with quantum wells and quantum dots of types I and II, in two-dimensional transition metals dichalcogenides and quantum microcavities. The basic mechanisms of the magnetic circular polarization of luminescence are considered. It is shown that either known mechanisms should be modified or additional mechanisms of the MCPL should be developed to describe the polarized photoluminescence in newly invented nanosystems.

Kinematical Analysis of the Evolution of Reflection High Energy Electron Diffraction Patterns of Quantum Dot Heterostructures: Correlation with Strain and Anisotropy

2006 ◽  
Vol 924 ◽  
Author(s):  
Andrea Feltrin ◽  
Alexandre Freundlich
Keyword(s):  
Quantum Dots ◽  
Electron Diffraction ◽  
Quantum Dot ◽  
Three Dimensional ◽  
High Energy ◽  
Image Features ◽  
Energy Electron ◽  
Clear Correlation ◽  
High Energy Electron ◽  
Strain Anisotropy

ABSTRACTThe strain distributions and of reflection high energy electron diffraction (RHEED) patterns of uncapped pyramidal shape InAs Stranski-Krastanov quantum dots fabricated on GaAs(001) substrate are investigated theoretically. The three dimensional strain anisotropy is computed with an atomistic elasticity approach, using inter-atomic Keating potentials and the strain energy is minimized using the conjugate gradient numerical method. RHEED images are predicted in the framework of the kinematical theory, by taking into account the refraction of the electron beam at the quantum dot/vacuum interface. Clear correlation between RHEED image features and quantum dot structural properties is established. The study stresses the potential of RHEED for future experimental real-time (during growth) detections and deciphering of strain anisotropies in quantum dots.

Metalorganic vapor phase epitaxial growth of GaInN/GaN hetero structures and quantum wells

1996 ◽  
Vol 449 ◽  
Author(s):  
F. Scholz ◽  
V. HÄrle ◽  
F. Steuber ◽  
A. Sohmer ◽  
H. Bolay ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Vapor Phase ◽  
High Energy ◽  
Smooth Transition ◽  
Nucleation Layer ◽  
Time Resolved ◽  
Transmission Electron ◽  
Energy Peak ◽  
Scanning Transmission ◽  
Composition Fluctuations

ABSTRACTGaInN/GaN heterostructures and quantum wells have been grown by low pressure metalorganic vapor phase epitaxy on sapphire using an AIN nucleation layer. We found a significant In incorporation only for growth temperatures of 700°C, although still very high In/Ga ratios in the gas phase had to be adjusted. The In content could be increased by reducing the H2/N2 flow ratio in the main carrier gas. GaInN layers typically show two lines in low temperature photoluminescence which are identified as excitonic-like (high energy peak) and impurity-related-like (low energy) by time-resolved spectroscopy. Quantum wells with a thickness between 8 and 0.5 nm showed only one emission line. The peak of the thinnest wells shows excitonic-like behaviour, whereas we found a smooth transition to an impurity-related-like type with increasing thickness. By scanning transmission electron microscopy studies we found indications for composition fluctuations in these thicker quantum wells which may cause localization effects for the excitons and thus be responsible for the observed optical spectra.

Low-dimensional effects in a three-dimensional system of Si quantum dots modified by high-energy ion irradiation

2009 ◽  
Vol 20 (18) ◽  
pp. 185401 ◽  
Author(s):  
I V Antonova ◽  
A G Cherkov ◽  
V A Skuratov ◽  
M S Kagan ◽  
J Jedrzejewski ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Ion Irradiation ◽  
Three Dimensional ◽  
High Energy ◽  
Dimensional System ◽  
Dimensional Effects ◽  
Low Dimensional ◽  
Si Quantum Dots ◽  
Three Dimensional System

Magnetoexciton states and diamagnetic shifts in quantum dots/ultrathin quantum wells under growth-direction magnetic fields

2008 ◽  
Vol 39 (3-4) ◽  
pp. 348-350 ◽  
Author(s):  
Z. Barticevic ◽  
M. Pacheco ◽  
C.A. Duque ◽  
L.E. Oliveira
Keyword(s):  
Quantum Dots ◽  
Magnetic Fields ◽  
Quantum Wells ◽  
Growth Direction
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