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5 Acta Physica Polonica A

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Relationship between Sample Morphology and Carrier Diffusion Length in GaN Thin Films

100%

Godlewski M. , Goldys E. , Phillips M. , Böttcher T. , Figge S. , Hommel D. , Czernecki R. , Prystawko P. , Leszczynski M. , Perlin P. , Wisniewski P. , Suski T. , Bockowski M. , Grzegory I. , Porowski S.

Acta Physica Polonica A

2002

tom 102

nr 4-5

627-632

Scanning and spot-mode cathodoluminescence investigations of homo- and hetero-epitaxial GaN films indicate a surprisingly small influence of their microstructure on overall intensity of a light emission. This we explain by a correlation between structural quality of these films and diffusion length of free carriers and excitons. Diffusion length increases with improving structural quality of the samples, which, in turn, enhances the rate of nonradiative recombination on structural defects, such as dislocations.

Cathodoluminescence Profiling of InGaN-Based Quantum Well Structures and Laser Diodes - In-Plane Instabilities of Light Emission

100%

Godlewski M. , Ivanov V. , Goldys E. , Phillips M. , Böttcher T. , Figge S. , Hommel D. , Czernecki R. , Prystawko P. , Leszczynski M. , Perlin P. , Grzegory I. , Porowski S.

Acta Physica Polonica A

2003

tom 103

nr 6

689-694

Instabilities of light emission and also of stimulated emission in series of GaN epilayers and InGaN quantum well structures, including laser diode structures, are studied. A stimulated emission is observed under electron beam pumping. This enabled us to study light emission properties from laser structures and their relation to microstructure details. We demonstrate large in-plane fluctuations of light emission and that these fluctuations are also present for excitation densities larger than the threshold densities for the stimulated emission.

Localization Effects in GaN/AlGaN Quantum Well - Photoluminescence Studies

100%

Chwalisz B. , Wysmołek A. , Bożek R. , Korona K. , Stępniewski R. , Knap W. , Pakuła K. , Baranowski J. , Grandjean N. , Massies J. , Prystawko P. , Grzegory I.

Acta Physica Polonica A

2003

tom 103

nr 6

573-578

Exciton localization in GaN/AlGaN quantum well structures is studied by photoluminescence. An anomalous temperature behavior of the photoluminescence from the quantum well is observed. With increasing temperature the energy position of the excitonic emission line first decreases up to 20 K, then increases, reaching a maximum around 90 K, and then decreases again in the higher temperature range. The observed behavior is discussed in terms of localization at the interface potential fluctuations. It is argued that the temperature activated migration and subsequent release of the excitons from traps that occurs between 20 K and 90 K are responsible for the observed S-like shape of the energy dependence. The obtained results allow a direct characterization of the energy fluctuations present in GaN/AlGaN quantum wells grown by different techniques.

Crack Free GaInN/AlInN Multiple Quantum Wells Grown on GaN with Strong Intersubband Absorption at 1.55μm

100%

Cywiński G. , Skierbiszewski C. , Feduniewicz-Żmuda A. , Siekacz M. , Nevou L. , Doyennette L. , Julien F. , Prystawko P. , Kryśko M. , Grzanka S. , Grzegory I. , Porowski S.

Acta Physica Polonica A

2006

tom 110

nr 2

175-181

Crack free GaInN/AlInN multiple quantum wells were grown by rf plasma-assisted molecular beam epitaxy on (0001) GaN/sapphire substrates. The strain-engineering concept was applied to eliminate cracking effect for growth of intersubband structures on GaN. Indium contained ternary compounds of barrier and well layers are contrary strained to the substrate material. A series of crack free GaInN/AlInN intersubband structures on (0001) GaN was fabricated and investigated. The assumed composition and layered structure were confirmed by room temperature photoluminescence and X-ray diffraction measurements. The intersubband measurements were done in multipass waveguide geometry by applying direct intersubband absorption and photoinduced intersubband absorption measurements. The optimized structure design contains forty periods of Si-doped GaInN/AlInN quantum wells and exhibits strong intersubband absorption.

Polarity Related Problems in Growth of GaN Homoepitaxial Layers

100%

Leszczyński M. , Prystawko P. , Śliwinski A. , Suski T. , Litwin-Staszewska E. , Porowski S. , Paszkiewicz R. , Tłaczała M. , Beaumont B. , Gibart P. , Barski A. , Langer R. , Knap W. , Frayssinet E.

Acta Physica Polonica A

1998

tom 94

nr 3

427-430

Homoepitaxial layers of GaN were grown by metalorganic chemical vapour deposition on single crystals obtained by high-pressure, high-temperature technology. For each metalorganic chemical vapour deposition run, four samples were placed, (00.1) and (00.1̲) faces of the Mg-doped insulating and undoped highly-conductive substrates. The layers were examined using X-ray diffraction, photoluminescence and far-infrared reflectivity. It was found that the (00.1̲) easier incorporates donors resulting in higher free-electron concentrations in the layers grown on these sides of the crystals, both, undoped and Mg-doped.