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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.

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Optical methods used to optimise semiconductor laser structures with tunnel injection from quantum well to InGaAs/GaAs quantum dots

Rudno-Rudzinski W., Ryczko K., Sęk G., Syperek M., Misiewicz J., Pavelescu E. M., Gilfert C., Reithmaier J. P.

Optica Applicata

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2009

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Vol. 39, nr 4

923-932

EN

We present the results of optical measurements performed on structures consisting of an InGaAs quantum well (QW), separated by a thin barrier from a layer of self-assembled InGaAs quantum dots (QDs). Such a kind of design is called a tunnel injection structure, because its functionality is based on the tunnelling of carriers from a QW to QDs, preferably with the assistance of optical phonons. In this approach, the injector QW serves as a reservoir of the carriers (due to much higher efficiency of carrier collection) and alleviates the problem of long relaxation times needed for carriers to reach the QDs ground state. In order to investigate the structures several complementary experimental techniques are applied. Photoreflectance, an absorption-like modulation spectroscopy, gives the information about the optical transitions and the electronic structure. The temperature evolution of photoluminescence allows emission efficiency and carrier losses to be determined. Photoluminescence excitation probes directly the carrier transfer from QW to the dots. The interpretation of the results is supported by the calculations in the envelope function formalism. It has been found out that the wavefunction position of the lowest lying levels depends on the QW parameters and thus different regimes of tunnelling are proposed.

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Photoreflectance spectroscopy of thick GaN layers grown by hydride vapour phase epitaxy technique

Syperek M., Kudrawiec R., Misiewicz J., Korbutowicz R., Paszkiewicz R., Tłaczała M.

Optica Applicata

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2005

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Vol. 35, nr 3

529-535

EN

The room temperature photoreflectance (PR) spectroscopy was used to investigate thick GaN epitaxial layers. The GaN layers were grown by hydride vapour phase epitaxy (HVPE) technique and compared to thin GaN layer grown by metalorganic vapour phase epitaxy (MOVPE) technique on AlN buffer layer. We observed energy red shift of the PR resonance for HVPE GaN layers compared with MOVPE GaN layer. This blue shift is due to reduction of the strain in HVPE layer. In addition, weak PR features related to Franz-Keldysh oscillations (FKO) have been observed. The electric field determined from the FKO period is 28 and 71 kV/cm for MOVPE and HVPE layers, respectively.

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Photoreflectance and photoluminescence of thick GaN layers grown by HVPE

Kudrawiec R., Korbutowicz R., Paszkiewicz R., Syperek M., Misiewicz J.

Opto-Electronics Review

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2004

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Vol. 12, No. 4

435-439

EN

Very thick (up to 100 µm) GaN layers grown by HVPE are investigated by photoreflectance (PR) and photoluminescence (PL) spectroscopies. The layers were deposited on a GaN buffer layer which was grown on a c-plane sapphire substrate by MOVPE. Both, N- and Ga-polar layers were selected to these investigations. We have observed a strong dependence of the optical properties on the polarity of GaN surface. We have obtained that the bandgap-related emission for Ga-polar layers is stronger and narrower than the emission for N-polar layers. Also, significant differences have been found in PR spectra of the two type layers. In the case of Ga-polar layer a broad PR resonance with Franz-Keldysh oscillation (FKO) related to the surface electric field (215 kV/cm) has been observed, while in the case of N-polar layer narrow resonances have been found as being predominant. No-FKO for N-polar layer indicates that the surface electric field for this layer is weak. It means that the surface barrier for N-polar GaN is much smaller than for Ga-polar GaN layer.