Understanding the mechanisms of energy transfer between the elements of heterostructures used in optoelectronics is essential for optimizing the design of the devices. This problem is being actively studied at various types of objects [1–4]. The transfer of excitons and carriers as well as the dipole-dipole FÖrster type transfer [5] are possible.

The low-temperature photoluminescence (PL) and PL excitation (PLE) spectra of two systems of CdTe quantum wells (QWs) separated by CdMnTe and CdMgTe barriers 20 nm thick are studied. The experimental PL spectra are compared with calculations that take into account the exciton effect and the influence of internal strains. The scatter of our data does not exceed that expected for monolayer fluctuations of the QW width. In the PLE spectra of a thick QW, bands were found that correspond to the increase of PL from a thick QW upon excitation of a neighbor narrow QW. The mechanism of energy transfer between QWs separated by thick barriers is discussed.

The reflection and luminescence spectra of a CdTe/CdMgTe heterostructures doped with iodine are studied. Iodine was introduced either into a barrier layer or into a wide CdTe quantum well. It is shown how the doping method and level affect the spectra and the temperature dependence of the quantum well exciton emission intensity. Keywords: heterostructure CdTe/CdMgTe, doping, exciton, luminescence.

Reflection, luminescence (PL), and luminescence excitation (PLE) spectra of a CdTe/CdMnTe heterostructure with quantum wells of different thicknesses are studied. It has been found that at low temperatures light emission comes from localized exciton states of quantum wells. The PLE spectra show that the contributions of excitons and free carriers to the population of quantum well depend on its thickness. The ratio of these contributions affects the dependence of the quantum well luminescence intensity on the level of optical excitation. It has been established that the coupling of quantum wells, separated by thick barrier layers, occurs through exciton excited states.

The reflection and luminescence spectra of a CdTe/CdMgTe heterostructures doped with iodine are studied. Iodine was introduced either into a barrier layer or into a wide CdTe quantum well. It is shown how the doping method and level affect the spectra and the temperature dependence of the quantum well exciton emission intensity.

A series of heterostructures consisting of a ZnTe matrix containing two CdTe monolayers separated by barrier layers of different thicknesses is studied. The dependences of the energies of the exciton radiation bands associated with narrow-band CdTe layers, their relative intensities, and temperature behavior on the thickness of the ZnTe barrier layer are determined. It is established that at a barrier layer thickness of more than 30 monolayers CdTe monolayers can be considered independent of each other.

The luminescence, reflection and absorption spectra of layered BiI3 crystals on samples of different quality are studied in a wide temperature range. Based on the data obtained, the parameters of the direct exciton, which has a high oscillator strength, are estimated. Keywords: Bismuth(III) iodide, exciton, localized states

The luminescence, reflection and absorption spectra of layered BiI3 crystals on samples of different quality are studied in a wide temperature range. Based on the data obtained, the parameters of the direct exciton, which has a high oscillator strength, are estimated

The aim of this work was to grow and study the optical properties of heterostructures with ultrathin inclusions at interfaces, which improve the quality of interfaces.

The photoluminescence (PL) and PL excitation (PLE) spectra of CdTe/ZnTe asymmetric double quantum well (QW) structures are studied on a series of samples containing two CdTe layers with nominal thicknesses of 2 and 4 monolayers (ML) in the ZnTe matrix. The samples differ in the thickness of the ZnTe spacer between CdTe QWs which is 45, 65 and 75 ML. It has been found that at above-barrier excitation the PL from a shallow QW at sufficiently weak excitation intensities is determined by recombination of hot excitons. It is shown that under these conditions, when PL is excited by lasers with different wavelengths, the ratio of the PL intensities from shallow and deep QWs decreases exponentially with an increase of the initial kinetic energy of hot excitons. It is found that energy relaxation of hot excitons with LO phonon emission determine the shape of the PLE spectrum of shallow QW in the range of exciton kinetic energies up to more than 20 LO phonons above ZnTe bandgap. We have shown that the results obtained are well described by the model of charge and energy transfer between QWs.

A series of ZnTe matrix containing two CdTe monolayers separated by barrier layers of different thicknesses is studied. The dependences of the energies of the exciton emission bands related to the CdTe monolayers, their relative intensities, and temperature behavior on the thickness of the ZnTe barrier layer are determined. It is established that CdTe monolayers can be considered independent of each other with a barrier layer thickness of more than 30 monolayers.

The photoluminescence (PL) spectra of CdTe/ZnTe double quantum wells (QWs) are studied on a series of samples containing two CdTe layers with nominal thicknesses of 2 and 4 monolayers (ML) in the ZnTe matrix. The QWs were grown in atomic-layer epitaxy and separated by ZnTe spacers with the thicknesses d sp =40−160 ML. The dependences of the relative intensity of shallow QW 1 and deep QW 2 PL bands ( I 1 and I 2 , respectively) on the pump intensity (J) when excited by the lasers with different radiation wavelengths are investigated. It is found that in the sample with d sp =40 ML, the ratio Y(J)=I 1 /I 2 depends on J and the shape of the Y ( J ) dependency changes with the excitation wavelength. In the samples with d sp > 70 ML Y ( J ) also changes with the excitation intensity J, but the shape of this dependence is the same for various excitation wavelengths. It is concluded that the energy relaxation in these samples is influenced not only by the tunneling of charge carriers from QW 1 to QW2, but also by carrier relaxation at the nonradiative centers, for which the recombination rate is different for shallow and deep QWs.

Heterostructures with atomically thin double quantum wells based on CdTe/ZnTe are investigated by optical spectroscopy (photoluminescence and reflectivity methods) as a function of temperature and density of excitation. Heavy and light exciton luminescence lines are observed with comparable intensities and different temperature behaviors (they cross each other at about 65° K). All these features agree with a complete calculation that takes into account both a very small chemical band offset for such monolayer CdTe inclusions in the ZnTe matrix (namely, 2%), and, consequently, the importance of Coulombic interaction in these double quantum wells.

Abstract Heterostructures of the CdTe/ZnTe type with ultrathin quantum wells are studied. Lines of light and heavy excitons bound to the CdTe layers are observed in the spectra. It is found that the photoluminescence intensity of the light exciton is comparable to the luminescence intensity of the heavy exciton. The temperature shifts of these lines are different, and the lines are intersected at a temperature of 65 K. The estimates of the energy and wave functions of the exciton states have made it possible to clarify parameters of some bands and excitons in such structures.

Reflectivity and modulated photoreflectivity spectra of ZnO and Zn1 – xMgxO epitaxial layers as well as ZnO/Zn1 – xMgxO quantum wells have been studied at normal and oblique light incidence. Comparison of experimental and calculated spectra allowed refinement of certain parameters of excitons in these structures and the order of energy bands in ZnO.

Изучена экситонная фотолюминесценция оксида цинка в температурном интервале 5-300 K. Проведен анализ формирования контура полосы экситонного излучения при 300 K и возбуждении He-Cd-лазером в спектрах нелегированных кристаллов, порошка марки ОСЧ и тонких ALD-пленок толщиной 4-450 nm. Исследовано влияние процессов фотодесорбции и фотоадсорбции атмосферного кислорода на спектр экситонного излучения порошка ZnO в последовательных циклах смены среды вакуум--воздух при комнатной температуре и непрерывном возбуждении He-Cd-лазером. Ключевые слова: экситонное излучение, фотоадсорбция, фотодесорбция, экситон-фононное взаимодействие.

Исследованы спектры отражения и модуляционного фотоотражения от эпитаксиальных слоев ZnO и Zn1-xMgxO, а также квантовых ям ZnO/Zn1-xMgxO при нормальном и наклонном падении света. Сравнение экспериментально измеренных и расчетных спектров позволило уточнить некоторые параметры экситонов в этих структурах и уточнить порядок следования энергетических зон в ZnO. Ключевые слова: гетероструктуры, квантовые ямы, экситоны, спектроскопия.

Heterostructures of the CdTe/ZnTe type with ultrathin quantum wells are studied. Lines of light and heavy excitons bound to the CdTe layers are observed in the spectra. It is found that the photoluminescence intensity of the light exciton is comparable to the luminescence intensity of the heavy exciton. The temperature shifts of these lines are different, and the lines are intersected at a temperature of 65 K. The estimates of the energy and wave functions of the exciton states have made it possible to clarify parameters of some bands and excitons in such structures.

The exciton photoluminescence of zinc oxide is studied in the temperature range 5–300 K. The formation of the exciton emission band profile in the spectra of undoped crystals, high-purity powder, and thin ALD films 4–450 nm in thickness at 300 K and at excitation by a He–Cd laser is analyzed. The effects of the photodesorption and photoadsorption of atmospheric oxygen on the exciton emission spectrum of a ZnO powder in sequential vacuum–air cycles have been studied at room temperature during continuous excitation by a He–Cd laser.

The luminescence of CdTe layers with a nominal thickness of 1, 2, 4, and 8 monolayers grown by atomic layer epitaxy in ZnTe matrix was studied. It is shown that layers with a thickness of 1 and 2 monolayers are homogeneous, while layers with a nominal thickness of 4 and 8 monolayers are the planar QD arrays. The sizes of QDs and their size dispersion increase with an increase in the nominal thickness of CdTe layer. The luminescence excitation spectra of CdTe layer in the samples vary significantly. It has been shown that, depending on the energy distance between the CdTe and ZnTe exciton levels, the ratio of contributions to the energy transfer via the exciton ZnTe and charge carriers varies greatly.