The role of surface phonons in the formation of the spectrum of polaron states in quantum dots
- PDF / 198,016 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 77 Downloads / 167 Views
DIMENSIONAL SYSTEMS
The Role of Surface Phonons in the Formation of the Spectrum of Polaron States in Quantum Dots A. Yu. Maslov^, O. V. Proshina, and A. N. Rusina Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia ^e-mail: [email protected] Submitted October 30, 2006; accepted for publication November 28, 2006
Abstract—The theory of large-radius polarons in quantum dots is developed with the difference in dielectric properties between the materials of the quantum dot and surrounding matrix taken into consideration. It is shown that the magnitude of the polaron effect is essentially dependent on the spectrum of surface optical phonons. The polaron shift of the size-quantized energy levels for electrons and holes is determined taking into account their interaction with phonons in the bulk and surface phonons. The conditions in which the interaction with surface phonons prevails are defined. It is shown that, in the II–VI compounds, the energy of the interaction can be higher than 10 meV and, hence, should be taken into account in calculating the energy spectrum. An approximate method for treating the polaron states is developed. The method provides a means for determining the magnitudes of the polaron shift in differently arranged heterostructures. It is found that the results obtained for the effect of surface phonons on the polaron states by the approximate method and by exact calculations are in good agreement. PACS numbers: 63.22.+m, 71.38.-k, 71.45.Gm, 73.21.-b DOI: 10.1134/S1063782607070093
In the last few years, the electronic properties of quantum nanostructures have been the subject of extensive studies. One of the important consequences of the confinement of charge carriers in nanostudtures is the quantization of the energy spectrum of charge carriers. The phonon properties of low-dimensional systems have been studied in less detail. At the same time, it is known that the difference between the dielectric properties of the materials used as a basis for producing such structures modifies the phonon spectra of the bulk and initiates additional vibrational excitations, surface phonons (interfacial phonons). In addition, the strength of the electron–phonon interaction is changed. This can result in substantial changes in the energies of the sizequantized levels of charge carriers. In this case, the interaction of charged particles with polar optical phonons in quantum dots (QDs) fabricated from materials with a high degree of ionicity is of greatest interest. This is because such interaction can be strong even in bulk materials [1], being substantially enhanced by lowering of the effective dimensionality of the nanostructure [2]. Since the states of charge carriers in a QD are localized, their interaction with polar optical phonons (the polaron effect) manifests itself in the change in the energy position of the size-quantized levels. In this study, we treat the polaron effect in QDs theoretically, taking into account the influence of both bulk and surface phon
Data Loading...
