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- ItemNucleation chronology and electronic properties of In(As,Sb,P) graded composition quantum dots grown on InAs(100) substrate(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Gambaryan, Karen M.; Boeck, Torsten; Trampert, Achim; Marquardt, OliverWe provide a detailed study of nucleation process, characterization, electronic and optical properties of graded composition quantum dots (GCQDs) grown from In-As-Sb-P composition liquid phase on an InAs(100) substrate in the Stranski-Krastanov growth mode. Our GCQDs exhibit diameters from 10 to 120 nm and heights from 2 to 20 nm with segregation profiles having a maximum Sb content of approximately 20% at the top and a maximum P content of approximately 15% at the bottom of the GCQDs so that hole confinement is expected in the upper parts of the GCQDs. Using an eight-band k · p model taking strain and built-in electrostatic potentials into account, we have computed the hole ground state energies and charge densities for a wide range of InAs1-x-ySbxPy GCQDs as close as possible to the systems observed in experiment. Finally, we have obtained an absorption spectrum for an ensemble of GCQDs by combining data from both experiment and theory. Excellent agreement between measured and simulated absorption spectra indicates that such GCQDs can be grown following a theory-guided design for application in specific devices.
- ItemNumerical cooling strategy design for hot rolled dual phase steel(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2010) Suwanpinij, Piyada; Togobytska, Nataliya; Prahl, Ulrich; Weiss, Wolf; Hömberg, Dietmar; Bleck, WolfgangIn this article, the Mo-Mn dual phase steel and its process parameters in hot rolling are discussed. The process window was derived by combining the experimental work in a hot deformation dilatometer and numerical calculation of process parameters using rate law models for ferrite and martensite transformation. The ferrite formation model is based on the Leblond and Devaux approach while martensite formation is based on the Koistinen-Marburger (K-M) formula. The carbon enrichment during ferrite formation is taken into account for the following martensite formation. After the completion of the parameter identification for the rate law model, the evolution of phases in multiphase steel can be addressed. Particularly, the simulations allow for predicting the preferable degree of retained strain and holding temperature on the run out table (ROT) for the required ferrite fraction.
- ItemTraveling wave modeling, simulation and analysis of quantum-dot mode-locked semiconductor lasers(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2010) Radziunas, Mindaugas; Vladimirov, A.G.; Viktorov, E.A.We analyze the dynamics of a mode-locked quantum-dot edge-emitting semiconductor laser consisting of reversely biased saturable absorber and forward biased amplifying sections. To describe spatial non-uniformity of laser parameters, optical fields and carrier distributions we use the traveling wave model, which takes into account carrier exchange processes between wetting layer and quantum dots. A comprehensive parameter study and an optical mode analysis of operation regimes are presented.
- ItemStrong asymmetry of mode-locking pulses in quantum-dot semiconductor lasers(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2010) Radziunas, Mindaugas; Vladimirov, Andrei G.; Viktorov, Evgeny A.; Fiol, Gerrit; Schmeckebier, Holger; Birnmberg, DieterWe describe the formation of a strong pulse asymmetry in mode-locked quantum-dot edge-emitting two-section semiconductor lasers. A mode decomposition technique reveals the role of the superposition of different modal groups. The results of theoretical analysis are supported by experimental data.