<i>In-situ</i>height engineering of InGaAs / GaAs quantum dots by chemical beam epitaxy

This special section of the Journal of Nanophotonics is focused on optics, spectroscopy, and nanophotonics of quantum dots.The study of optical properties of colloidal quantum dots (QDs) and nanostructures, which are formed based on them, is actual for modern nanophotonics.Interest in these structures is caused by the widest range of practical applications in various fields.The most actual applications of photonics of QDs are fluorescent labeling of biological objects, biosensors, and minimally invasive biomedical technology, including thermal and photodynamic therapy of severe human diseases.[1][2][3] Primarily, the unique optical properties of colloidal QDs are sizedependent optical absorption and photoluminescence spectra, a wide range of luminescence excitation, high photostability of nanocrystals, etc.These properties of colloidal QD spectroscopy provide opportunities for the development of optically distinguishable codes, identifying various diseases, markers of diseased cells, tissues, and organs with its subsequent visualization.The possibility of specific binding of bioconjugated QDs with different targets provide opportunities for labeling of cells and a variety of protein molecules both in vitro and in vivo.The basis of marked applications is fundamental processes.They are [1][2][3] : absorption of light by colloidal QDs; the formation of excitons; radiative and nonradiative annihilation of excitons; radiative recombination of localized excitons; relations of processes of recombination luminescence with QD size and their composition (special in the case of substitutional solid solutions); the exchange of electronic excitations between colloidal QDs and organic structures, which interact with interface of quantum dots.Thus, the authors' papers 1-3 develop these important areas of optics and spectroscopy of colloidal quantum dots.A simple model of a quasi-zero-dimensional structure in the form of a spherical QD of radius a and permittivity ε 2 , embedded in a medium with permittivity ε 1 , was discussed in Ref. 4. An electron (e) and a hole (h) with effective masses m e and m h were assumed to travel within the QD.We assume that the permittivities satisfy the relation ε 2 ≫ ε 1 and that the conduction and valence bands are parabolic.The theory of exciton states in QDs under conditions of dominating polarization interaction of an electron and a hole with a spherical (QDdielectric matrix) interface are developed in Ref. 4. It is shown that the energy spectrum of a heavy hole in the valence band QD is equivalent to the spectrum of a hole carrying out oscillator vibrations in the adiabatic electron potential.5 It is shown that the absorption and emission edge of QDs is formed by two transitions of comparable intensity from different hole size-quantization levels and into a lower electron size-quantization level.6 The interband absorption of light in QDs was studied theoretically in Ref. 6 using the dipole approximation in the framework of the model [4] considered here, and under the assumption that the absorption length λ ≫ a.An expression for the quantity Kðs; ωÞ defined by the hole optical transition from the energy level t h ¼ 2n h (t h is the hole main quantum number, n h , is the hole radial quantum number) to the lowest electron level (n e ¼ 1, l e ¼ m e ¼ 0) (here

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