Wyniki wyszukiwania - Biblioteka Nauki

1

Optical properties of nominally undoped n-type MOVPE GaN epilayers

100%

Kudrawiec R. , Misiewicz J. , Paszkiewicz R. , Paszkiewicz B. , Tłaczała M.

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tom Vol. 32, nr 3

381-388

EN

Nominally undoped GaN epilayers have been grown by the metalorganic vapour phase epitaxy (MOVPE) technique on (0001) sapphire substrates. Various growth conditions result in different concentration of defects, which is strongly correlated with the electron concentration. For epilayers selected to these investigations the electron concentration changes from 5×1015 cm–3 to 5×1018 cm–3. The optical methods like photoluminescence (PL), reflectance (R) and photoreflectance (PR) have been applied to define a correlation between quality and electron concentration of the GaN epilayer. It has been found that an improvement of optical properties, which is always associated with the improvement of the sample quality, appears to be connected with the decrease in electron concentration. The existence of free excitons has been observed for epilayer with the electron concentration lower than 1017 cm–3.

2

Photoreflectance study of partially relaxed epitaxial InGaAs on GaAs

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Motyka M. , Gelczuk Ł. , Dąbrowska-Szata M. , Serafinczuk J. , Kudrawiec R. , Misiewicz J.

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2009

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tom Vol. 39, nr 3

561-570

EN

Room temperature photoreflectance (PR) spectroscopy and high resolution X-ray diffraction (HRXRD) have been used to investigate InxGa1-xAs layers grown compressively by MOVPE on GaAs substrates, with different composition and thickness. HRXRD reveals that all the samples are partially relaxed and In composition has been determined for each of the samples. The effects of residual strain on the optical response of the samples, namely interband transitions and the valence band splitting, were analyzed by fitting the standard line shape form to the PR data. The energies determined experimentally as a function of indium content were compared to those obtained in the framework of the elastic strain theory for pseudomorphic layers. This comparison allows us to estimate the extent of strain relaxation and to determine the residual strain values in the samples. Furthermore, we revealed that the measured residual strain ?res follows t-1/2 dependence on the epitaxial layers thickness t. This confirms the appropriateness of the nonequilibrium models (energy-balance models) for these structures.

3

Planarne domieszkowanie krzemem naprężonych studni kwantowych InxGa1-xAs/GaAs w technice MOVPE

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Ściana B. , Radziewicz D. , Paszkiewicz B. , Tłaczała M. , Sitarek P. , Kudrawiec R. , Misiewicz J. , Kováč J. , Florovič M.

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tom Vol. 46, nr 2-3

14-15

PL

Przedstawiono wyniki badań, dotyczące procesów planarnego domieszkowania krzemem naprężonych, pojedynczych studni kwantowych InxGa1-xAs/GaAs w technice MOVPE. Badano wpływ parametrów procesu domieszkowania oraz szerokości studni kwantowej na rozkład domieszki krzemowej. Wprowadzenie domieszki typu delta do studni kwantowej w znaczący sposób zwiększa jej przestrzenne ograniczenie. Ponadto powoduje silną modyfikację przejść optycznych i wzmocniony efekt Starka.

EN

This work presents the studies of Si-δ-doped InxGa1-x As/GaAs strained quantum well obtained by MOVPE technology. The influence of the growth parameters and quantum well width on silicon dopant distribution was investigated. It was shown that introducing delta layer into quantum well gives better carrier confinement. In addition, the PR and PC spectra of Si-δ-doped InxGa1-x As/GaAs SQW confirmed significant modification of the optical transitions and enhanced QCSE.

4

Technology and properties of low-pressure metalorganic vapour phase epitaxy grown InGaAs/AlInAs superlattice for quantum cascade laser applications

72%

Badura M. , Bielak K. , Ściana B. , Radziewicz D. , Pucicki D. , Dawidowski W. , Żelazna K. , Kudrawiec R. , Tłaczała M.

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tom Vol. 46, nr 2

241--248

EN

Quantum cascade laser is one of the most sophisticated semiconductor devices. The active region of the quantum cascade laser consists of hundreds thin layers, thus the deposition precision is the most crucial. The main technique for the fabrication of quantum cascade laser structure is molecular beam epitaxy, however, the prevalence of metalorganic vapour phase epitaxy techniques in the fabrication of semiconductor structures causes a perpetual work on the improvement production of the entire quantum cascade laser structure by the metalorganic vapour phase epitaxy. The paper presents technological aspects connected with the metalorganic vapour phase epitaxy growth of InGaAs/AlInAs low-dimensional structures for quantum cascade laser active region emitting ~9.6 μm radiation. Epitaxial growth of superlattice made of InGaAs/AlInAs lattice matched to InP was conducted at the AIXTRON 3x2″ FT system. Optical and structural properties of such heterostructures were characterised by means of high resolution X-ray diffraction, photoluminescence, contactless electroreflectance and scanning electron microscope techniques. Epitaxial growth and possible solutions of structure improvements are discussed.