Electron-hole correlations in semiconductor quantum dots with tight-binding wave functions - art. no. 195318

Citation
S. Lee et al., Electron-hole correlations in semiconductor quantum dots with tight-binding wave functions - art. no. 195318, PHYS REV B, 6319(19), 2001, pp. 5318
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICAL REVIEW B
ISSN journal
0163-1829 → ACNP
Volume
6319
Issue
19
Year of publication
2001
Database
ISI
SICI code
0163-1829(20010515)6319:19<5318:ECISQD>2.0.ZU;2-9
Abstract
The electron-hole states of semiconductor quantum dots are investigated wit hin the framework of empirical tight-binding descriptions for Si, as an exa mple of an indirect-gap material, and InAs and CdSe as examples of typical III-V and II-VI direct-gap materials. We significantly improve the energies of the single-particle states by optimizing tight-binding parameters to gi ve the best effective masses. As a result, the calculated excitonic gaps ag ree within 5% error with recent photoluminescence data for Si and CdSe but they agree less well for InAs. The electron-hole Coulomb interaction is ins ensitive to different ways of optimizing the tight-binding parameters. Howe ver, it is sensitive to the choice of atomic orbitals; this sensitivity dec reases with increasing dot size. Quantitatively, tight-binding treatments o f Coulomb interactions are reliable for dots with radii larger than 15-20 A ngstrom. Further, the effective range of the electron-hole exchange interac tion is investigated in detail. In quantum dots of the direct-gap materials InAs and CdSe, the exchange interaction can be long ranged, extending over the whole dot when there is no local (onsite) orthogonality between the el ectron and hole wave functions. By contrast, for Si quantum dots the extra phase factor due to the indirect gap effectively limits the range to about 15 Angstrom, independent of the dot size.