scholarly journals Pseudopotential study of electron-hole excitations in colloidal free-standing InAs quantum dots

2000 ◽  
Vol 61 (3) ◽  
pp. 1978-1991 ◽  
Author(s):  
A. J. Williamson ◽  
Alex Zunger
Keyword(s):  
Quantum Dots ◽  
Free Standing ◽  
Electron Hole ◽  
Inas Quantum Dots

Electronic-Structure Theory of Semiconductor Quantum Dots

MRS Bulletin ◽  
1998 ◽  
Vol 23 (2) ◽  
pp. 35-42 ◽  
Author(s):  
Alex Zunger
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Coulomb Blockade ◽  
Density Functional ◽  
Plane Waves ◽  
Electronic Structure Theory ◽  
Structure Theory ◽  
Free Standing ◽  
Electron Hole ◽  
Main Challenge

Progress made in the growth of “free-standing” (e.g., colloidal) quantum dots (see also articles in this issue by Nozik and Mićić, and by Alivisatos) and in the growth of semiconductor-embedded (“self-assembled”) dots (see also the article by Bimberg, Grundmann, and Ledentsov in this issue) has opened the door to new and exciting spectroscopic studies of quantum structures. These have revealed rich and sometimes unexpected features such as quantum-dot shape-dependent transitions, size-dependent (red) shifts between absorption and emission, emission from high excited levels, surface-mediated transitions, exchange splitting, strain-induced splitting, and Coulomb-blockade transitions. These new observations have created the need for developing appropriate theoretical tools capable of analyzing the electronic structure of 103–106-atom objects. The main challenge is to understand (a) the way the one-electron levels of the dot reflect quantum size, quantum shape, interfacial strain, and surface effects and (b) the nature of “many-particle” interactions such as electron-hole exchange (underlying the “red shift”), electron-hole Coulomb effects (underlying excitonic transitions), and electron-electron Coulomb (underlying Coulomb-blockade effects).Interestingly, while the electronic structure theory of periodic solids has been characterized since its inception by a diversity of approaches (all-electron versus pseudopotentials; Hartree Fock versus density-functional; computational schemes creating a rich “alphabetic soup,” such as APW, LAPW, LMTO, KKR, OPW, LCAO, LCGO, plane waves, ASW, etc.), the theory of quantum nano-structures has been dominated mainly by a single approach so widely used that I refer to it as the “Standard Model”: the effective-mass approximation (EMA) and its extension to the “k · p” (where k is the wave vector and p is the momemtum). In fact, speakers at nanostructure conferences often refer to it as “theory” without having to specify what is being done. The audience knows.

Acoustical plasma oscillations in photoexcited electron-hole plasma induced in GaAs layers embedded with InAs quantum dots

2000 ◽  
Vol 11 (4) ◽  
pp. 314-317 ◽  
Author(s):  
B H Bairamov ◽  
V A Voitenko ◽  
V V Toporov ◽  
B P Zakharchenya ◽  
M Henini ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Electron Hole ◽  
Photoexcited Electron ◽  
Plasma Oscillations ◽  
Inas Quantum Dots ◽  
Hole Plasma ◽  
Electron Hole Plasma

Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM

1990 ◽  
Vol 48 (4) ◽  
pp. 728-729
Author(s):  
M.J. Kim ◽  
L.C. Liu ◽  
S.H. Risbud ◽  
R.W. Carpenter
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Processing Technique ◽  
Internal Stresses ◽  
Electron Hole ◽  
Spatial Dimensions

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

Magnetotunneling spectroscopy imaging of electron wave functions in self-assembled InAs quantum dots

2001 ◽  
Vol 171 (12) ◽  
pp. 1365
Author(s):  
E.E. Vdovin ◽  
Yu.N. Khanin ◽  
Yu.V. Dubrovskii ◽  
A. Veretennikov ◽  
A. Levin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Wave Functions ◽  
Electron Wave ◽  
Inas Quantum Dots ◽  
Self Assembled
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