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Struktury kwantowe ZnMgO/ZnO/ZnMgO wykonywane metodą MBE

Kozanecki A., Sajkowski J., Stachowicz M., Przeździecka E., Syperek M.

Elektronika : konstrukcje, technologie, zastosowania

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2014

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Vol. 55, nr 9

13-15

PL

Tlenek cynku i struktury kwantowe ZnMgO/ZnO/ZnMgO uważane są za bardzo obiecujące materiały do zastosowań optoelektronicznych, ze względu na wartość przerwy energetycznej Eg > 3,3 eV i energię wiązania ekscytonu >60 meV. W tej pracy przedstawione zostaną wyniki naszych badań pojedyńczych studni (QW) i wielostudni kwantowych ZnMgO/ZnO/ZnMgO, otrzymywanych metodą epitaksji z wiązek molekularnych na różnych podłożach takich jak szafir. Zaprezentowane zostaną właściwości optyczne układów podwójnych studni kwantowych otrzymanych na podłożach szafirowych. Przedyskutowane zostaną mechanizmy oddziaływania między studniami, w szczególności zostanie pokazany wpływ sprzężenia między studniami na emisję ekscytonową.

EN

Zinc oxide is considered as a very attractive semiconductor for applications in optoelectronics, because of its wide band gap, Eg, of 3.3 eV and large exciton binding energy of 60 meV. ZnMgO alloy has been considered as a suitable material for the barrier layers in ZnMgO/ZnO/ZnMgO superlattice structures, because alloying of ZnO with MgO (Eg~7.7 eV) enables widening of the bandgap of ZnO up to at least 4.5 eV without loss of crystalline quality. In ZnMgO/ZnO/ZnMgO quantum wells the binding energy of excitons increases up to 100 meV which promises obtaining of efficient electroluminescence in devices operating on excitonic transitions at room temperature. In this presentation the results of our studies of single and multiple quantum well structures of ZnMgO/ZnO/ZnMgO grown by MBE on different sapphire will be presented. Optical properties of asymmetric coupled quantum wells grown on crystalline ZnO and on sapphire will be discussed. In particular, the influence of interwell coupling on the excitonic emission will be shown.

2

Selective infrared absorption and refraction of symmetrical two-layered molecular nanofilms

Rodic D, Skipina B, Pelemis S. S., Jacimovski S. K., Setrajcic J. P.

Optica Applicata

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2013

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Vol. 43, nr 4

641--649

EN

We have supplemented the already formulated microscopic theory of optical properties of very ultrathin molecular films (quantum nanofilms), i.e., quasi 2D systems parallel to XY planes bounded by two surfaces. The exposure of nanofilms to the external electromagnetic fields has resulted in the creation of excitons, but different than bulk ones in one direction perpendicular to surfaces. The analysis of the dielectric response of the system to perturbation of an external electromagnetic field shows that optical properties of these crystalline nanosystems for low exciton concentration of Frenkel’s excitons strongly depend on boundary parameters and the thickness of the film. In addition, the dynamical absorption and the refraction coefficient show a very narrow and discrete dependence of external electromagnetic field frequency, which is the consequence of both resonance and quantum size effects. Influences of boundary conditions on optical characteristics (through the analyses of dynamical absorption and refraction indices) of these nanostructures were specially and in details explored. The emission and the luminescence spectrum of the whole film have been analyzed and the results compared to experimental data show very good behavior and very good coordination.

3

Photoluminescence characterization of vacuum deposited PTCDA thin films

Bała W., Łukasiak Z., Rębarz M., Dalasiński P., Bratkowski A., Bauman D., Hertmanowski R.

Opto-Electronics Review

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2004

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Vol. 12, No. 4

445-448

EN

We investigated photoluminescence (PL) under steady state excitation and photoluminescence excitation (PLE) spectra of thin 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) films deposited on (001)Si substrate with various layer thicknesses grown at different substrate temperatures. The PL and PLE spectra have been measured at various temperatures, ranging from 10 K to 325 K. The PTCDA films exhibit strong luminescence at all mentioned ranges of temperature and for different values of excitation energy. The vibronic structure of PL spectra is clearly resolved at different temperatures. The position of peaks on energy scale depends on the temperature. We have observed a blue-shift of peaks with the decrease in the temperature. In all the investigated samples, the thermal quenching of PL has been observed. Analysis of the temperature dependence of the intensity bands, their position and full width half maximum (FWHM) allowed to find the energy barriers between the excited state and defect state. We propose a schematic potential energy diagram which explains mechanism of PL recombination

4

Exciton energies and probability of their radiative decay in GaN/AIN quantum structures

Tchelidze T., Kereselidze T.

Opto-Electronics Review

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2004

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Vol. 12, No. 4

441-443

EN

Exciton energies and probabilities of radiative transition from exciton state are calculated in GaN/AlN quantum dots. Electric field conditioned by strain induced and spontaneous polarization is considered by means of tight bind approximation, electron-hole Coulomb interaction is calculated by means of perturbation theory. Despite the presence of an electrical field, the calculated Coulomb energy is significantly increased with respect to bulk material. In large dots, the Coulomb term as well as probability of radiation transition for higher energetic excitons was strongly increased.