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22 results on '"Aschenbrenner, Timo"'

1. Optical Properties and Modal Gain of InGaN Quantum Dot Stacks

Author

Kalden, Joachim, Sebald, Kathrin, Gutowski, Juergen, Tessarek, Christian, Aschenbrenner, Timo, Figge, Stephan, and Hommel, Detlef

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We present investigations of the optical properties of stacked InGaN quantum dot layers and demonstrate their advantage over single quantum dot layer structures. Measurements were performed on structures containing a single layer with quantum dots or threefold stacked quantum dot layers, respectively. A superlinear increase of the quantum dot related photoluminescence is detected with increasing number of quantum dot layers while other relevant GaN related spectral features are much less intensive when compared to the photoluminescence of a single quantum dot layer. The quantum dot character of the active material is verified by microphotoluminescence experiments at different temperatures. For the possible integration within optical devices in the future the threshold power density was investigated as well as the modal gain by using the variable stripe length method., Comment: 9 Pages, 4 Figures

Published
2008
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6. Improved survival of patients with coronary artery disease and low ejection fraction with ICD implantation versus conventional therapy in a real world survey

Author

Aschenbrenner Timo, Brockmeier Johannes, Bramlage Peter, Fimmers Rolf, Cuneo Alessandro, Hochreuther Stefan, Zemmrich Claudia, and Tebbe Ulrich

Subjects
Implantable cardioverter defibrillator, Cohort study, Myocardial infarction, Medicine, Biology (General), QH301-705.5, Science (General), Q1-390
Abstract

Abstract Background Coronary artery disease (CAD) is associated with an increased risk for sudden cardiac death. Randomized controlled trials have shown that implantable cardioverter defibrillators (ICD) improve life expectancy unless they are implanted within the first days after an acute myocardial infarction and guidelines recommend their use. We aimed to validate that these results also apply to patients of a typical community hospital in Germany. Methods This was a retrospective analysis of patients undergoing coronary angiography in the Lippe-Detmold Hospital between 2003 and 2006. They had to have significant CAD and an ejection fraction (EF) ≤ 35% and no acute myocardial infarction within 28 days of implantation and no history of ventricular fibrillation. Results 213 patients were included; 70 of which received an ICD. Patients with an ICD implantation were younger (64.8 ± 9.9 vs. 67.9 ± 9.8 years; p = 0.034), had single vessel CAD more frequently (22.9 vs. 11.2%; p = 0.025) and a lower EF (26.7 ± 6.3 vs. 29.1 ± 4.6%; p = 0.006). Hospital readmissions were comparable between the ICD and the control group (68.6 vs. 72.0%; p = 0.602). ICD therapy was associated with a considerable survival benefit compared to conventional therapy (HR 0.52; 95%CI 0.29-0.93; p = 0.027) in a Cox-Proportional Hazards Regression analysis. Conclusions Appreciating the potential limitations of retrospective studies, we found that ICD use was associated with improved survival in patients with significant CAD and an EF

Published
2012
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7. Trap levels in the atomic layer deposition-ZnO/GaN heterojunction-Thermal admittance spectroscopy studies.

Author

Krajewski, Tomasz A., Stallinga, Peter, Zielony, Eunika, Goscinski, Krzysztof, Kruszewski, Piotr, Wachnicki, Lukasz, Aschenbrenner, Timo, Hommel, Detlef, Guziewicz, Elzbieta, and Godlewski, Marek

Subjects
GALLIUM nitride spectra, HETEROJUNCTIONS, ZINC oxide spectra, CONDUCTION bands, ELECTRIC conductivity
Abstract

In this work, a n-ZnO/p-GaN heterojunction is analyzed using admittance spectroscopy techniques. Capacitance transient measurements performed at 10 kHz reveal four majority-carrier deep levels, the most important one located at approximately 0.57 eV below the ZnO conduction band (CB) edge with a density about two orders of magnitude below the doping level (NT = 4 × 1015 cm-3). The others, located at 0.20 eV, 0.65 eV, and 0.73 eV, are about three orders of magnitude below the doping level (NT = 4-9 × 1014 cm-3). [ABSTRACT FROM AUTHOR]

Published
2013
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8. Growth and characterisation of nitrid-based semiconductors for opto-electronic applications: Nanorods, Bragg-reflectors and laserdiodes

Author

Aschenbrenner, Timo, Hommel, Detlef, and Rosenauer, Andreas

Subjects
AlInN, 530 Physics, growth, LED, epitaxy, Laser, quantum dots, GaN, DBR, MOVPE, x-ray, SEM, TEM, ddc:530, Nanorods
Abstract

Solid state light sources are present in applications such as Bluray-Players and they are used for communication via optical fiber networks. To achieve or to optimze these devices and to understand the physical properties of the group-III-nitride system fundamental research as well as device-orientated investigations are necessary. The work presented in this thesis was developed in this context. Four different epitaxial growth-topics were attended to. In all cases the final coal was to understand and to improve the growth mechanisms behind the optical devices of our future life. These topics range from the growth in non-polar direction to the realisation of catalyst- and mask-free grown, high quality nanorods. Besides, the work was concentrated on edge-emitting laser-structures, which were deposited on freestanding GaN-substrates and featured quantum dots as active material. Finally, the growth of AlInN-layers for an application in distributed Bragg mirrors was investigated.

Published
2010

9. Polytypism in GaAs nanowires: determination of the interplanar spacing of wurtzite GaAs by X-ray diffraction

Author

Köhl, Martin, primary, Schroth, Philipp, additional, Minkevich, Andrey A., additional, Hornung, Jean-Wolfgang, additional, Dimakis, Emmanouil, additional, Somaschini, Claudio, additional, Geelhaar, Lutz, additional, Aschenbrenner, Timo, additional, Lazarev, Sergey, additional, Grigoriev, Daniil, additional, Pietsch, Ullrich, additional, and Baumbach, Tilo, additional

Published
2015
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11. GaN tubes with coaxial non- and semipolar GaInN quantum wells

Author

Heinz, Dominik, primary, Fikry, Mohamed, additional, Aschenbrenner, Timo, additional, Schowalter, Marco, additional, Meisch, Tobias, additional, Madel, Manfred, additional, Huber, Florian, additional, Hocker, Matthias, additional, Frey, Manuel, additional, Tischer, Ingo, additional, Neuschl, Benjamin, additional, Mehrtens, Thorsten, additional, Müller, Knut, additional, Rosenauer, Andreas, additional, Hommel, Detlef, additional, Thonke, Klaus, additional, and Scholz, Ferdinand, additional

Published
2014
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20. Wachstum und Charakterisierung von nitrid-basierten Halbleiterstrukturen für optoelektronische Anwendungen: Nanosäulen, Bragg-Reflektoren und Laserdioden

Author

Aschenbrenner, Timo and Aschenbrenner, Timo

Abstract

Solid state light sources are present in applications such as Bluray-Players and they are used for communication via optical fiber networks. To achieve or to optimze these devices and to understand the physical properties of the group-III-nitride system fundamental research as well as device-orientated investigations are necessary. The work presented in this thesis was developed in this context. Four different epitaxial growth-topics were attended to. In all cases the final coal was to understand and to improve the growth mechanisms behind the optical devices of our future life. These topics range from the growth in non-polar direction to the realisation of catalyst- and mask-free grown, high quality nanorods. Besides, the work was concentrated on edge-emitting laser-structures, which were deposited on freestanding GaN-substrates and featured quantum dots as active material. Finally, the growth of AlInN-layers for an application in distributed Bragg mirrors was investigated.

21. Wachstum und Charakterisierung von nitrid-basierten Halbleiterstrukturen für optoelektronische Anwendungen: Nanosäulen, Bragg-Reflektoren und Laserdioden

Author

Aschenbrenner, Timo and Aschenbrenner, Timo

Abstract

Solid state light sources are present in applications such as Bluray-Players and they are used for communication via optical fiber networks. To achieve or to optimze these devices and to understand the physical properties of the group-III-nitride system fundamental research as well as device-orientated investigations are necessary. The work presented in this thesis was developed in this context. Four different epitaxial growth-topics were attended to. In all cases the final coal was to understand and to improve the growth mechanisms behind the optical devices of our future life. These topics range from the growth in non-polar direction to the realisation of catalyst- and mask-free grown, high quality nanorods. Besides, the work was concentrated on edge-emitting laser-structures, which were deposited on freestanding GaN-substrates and featured quantum dots as active material. Finally, the growth of AlInN-layers for an application in distributed Bragg mirrors was investigated.

22. Wachstum und Charakterisierung von nitrid-basierten Halbleiterstrukturen für optoelektronische Anwendungen: Nanosäulen, Bragg-Reflektoren und Laserdioden

Author

Aschenbrenner, Timo and Aschenbrenner, Timo

Abstract

Solid state light sources are present in applications such as Bluray-Players and they are used for communication via optical fiber networks. To achieve or to optimze these devices and to understand the physical properties of the group-III-nitride system fundamental research as well as device-orientated investigations are necessary. The work presented in this thesis was developed in this context. Four different epitaxial growth-topics were attended to. In all cases the final coal was to understand and to improve the growth mechanisms behind the optical devices of our future life. These topics range from the growth in non-polar direction to the realisation of catalyst- and mask-free grown, high quality nanorods. Besides, the work was concentrated on edge-emitting laser-structures, which were deposited on freestanding GaN-substrates and featured quantum dots as active material. Finally, the growth of AlInN-layers for an application in distributed Bragg mirrors was investigated.

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