Evolution of excitonic states in two-phase systems with quantum dots of II–VI semiconductors near the percolation threshold
✍ Scribed by N.V. Bondar; M.S. Brodyn
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 385 KB
- Volume
- 42
- Category
- Article
- ISSN
- 1386-9477
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✦ Synopsis
In two-phase disordered media composed of borosilicate glass with ZnSe or CdS quantum dots, the formation of a phase percolation transition of carriers for near-threshold concentrations that are manifested in optical spectra has been observed. Microscopic fluctuations of the quantum-dot density near the percolation threshold were found that resembled the phenomenon of critical opalescence, where similar fluctuations of the density of a pure substance appear near to a phase transition. It is proposed that the dielectric mismatch between a matrix and ZnSe or CdS quantum dots plays a significant role in the carrier (exciton) delocalization, resulting in the appearance of a ''dielectric Coulomb trap'' beyond the QD border and the formation of surface states of excitons. The spatial overlapping of excitonic states at the critical density of quantum dots results in a tunneling of carriers and the formation of a phase percolation transition in such media.