Home  About us  Contact
 

Quantum Dot Structures (quantum + dot_structure)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Contactless electroreflectance studies of II,VI nanostructures grown by molecular beam epitaxy

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004
Martín Muñoz
Abstract The interband transitions of a single quantum well structure of Zn0.53Cd0.47Se/Zn0.27Cd0.23Mg0.50Se, lattice matched to InP, and of a capped CdSe quantum dot structure have been investigated using contactless electroreflectance. From a comparison of the quantum well optical transitions with those calculated using the envelope function approximation we determined the band offsets for this system. The electroreflectance spectrum of the quantum dot structure shows transitions originating from all the portions of the sample including the quantum dots and the wetting layer. Assuming a lens shape geometry and that the effective height-to-radius ratio observed in uncapped quantum dots is preserved, the size of the capped quantum dots was determined using the observed electroreflectance transitions, and the effective mass approximation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Growth and characterization of bilayer InAs/GaAs quantum dot structures

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2006
B. L. Liang
Abstract One of the difficulties in understanding energy transfer in bilayer quantum dot structures is the complex role of carrier tunneling. This limitation is due to the fact that, for most studies to date, QDs in each layer have only one confined energy level making it difficult to study resonant tunneling effects. In this work, we have investigated the low growth-rate technique to produce dislocation-free very large QDs in the second layer that are characterized by several confined energy levels. The high quality surface morphology and optical behavior of these structures were demonstrated by AFM and PL measurements. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Phonons in InAs quantum dot structures

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2009
Alexander Milekhin
Abstract We present a Raman study of the phonon spectra of periodical structures with (In,Ga)As QDs in (Al,Ga)As matrix as well as AlAs QDs embedded in InAs grown by molecular beam epitaxy. Raman scattering by optical, interface and acoustic phonons was observed in the QD structures. TO and LO phonons in the QDs are strongly affected by both strain and confinement. The Raman study reveals a two-mode behavior of optical phonons in the whole composition range for both InGaAs QDs and the AlGaAs matrix. Raman scattering by InAs- and GaAs-like LO phonons in InGaAs QDs shows a size-selective resonant behaviour. Interface phonons were investigated in InGaAs QDs and the AlGaAs matrix. Their frequency positions were analyzed as a function of the alloy content within the dielectric continuum model. The positions of IF phonons in the QD structures observed in the experiment agree well with calculated ones assuming that the QDs have the shape of oblate ellipsoids. Multiple phonon Raman scattering involving both pure overtones of the first-order InAs, GaAs and AlAs optical and interface phonons and combination of phonons from the materials is observed in the vicinity with E0 resonance in QDs. Possible mechanisms of these processes are discussed. Low frequency resonant Raman scattering by acoustic phonons was observed in the QD structures. The periodic oscillations seen in the Raman spectra are well described by the elastic continuum model. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Spin-lattice relaxation in diluted magnetic (Cd,Mn)Se quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2005
A. Hundt
Abstract The dynamics of spin-lattice relaxation (SLR) is investigated in diluted magnetic (Cd,Mn)Se quantum dot structures with different Mn content by photo-carrier induced spin gas heating. The acquired time constants in the µs range show a strong dependence of the Mn content and of the temperature. There is no hint for a specific zero-dimensional behavior. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]