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Article
GaN based LED’s with different recombination zones
GaN based homo- and heterotype LED’s have been fabricated and characterized which emit in the blue and ultra-violet part of the spectral range. Complete epitaxial LED layer sequences with different recombinati...
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Article
Fundamentals, Material Properties and Device Performances in GaN MBE using On-Surface Cracking of Ammonia
Ammonia is investigated as nitrogen precursor for molecular beam epitaxy of group III nitrides. With the particular on-surface cracking approach, NH3 is dissociated directly on the growing surface. By this techni...
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Article
Efficient optical activation of ion-implanted Zn acceptors in GaN by annealing under 10 kbar N2 overpressure
We continue our investigations into the optical activation of Zn-implanted GaN annealed under ever higher N2 overpressure. The samples studied were epitaxial GaN/sapphire layers of good optical quality which were...
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Article
Improved optical activation of ion-implanted Zn acceptors in GaN by annealing under N2 overpressure
We investigated the properties of ion-implanted GaN:Zn annealed under various conditions using photoluminescence (PL) and high resolution x-ray diffraction (HRXRD). Epitaxial GaN/sapphire of high optical quali...
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Article
GaN Homoepitaxy for Device Applications
Epitaxial growth on GaN single bulk crystals sets new standards in GaN material quality. The outstanding properties provide new insights into fundamental material parameters (e.g. lattice constants, exciton bi...
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Chapter
Operating Principles of VCSELs
For some time already, vertical-cavity surface-emitting lasers (VCSELs) have emerged from being a laboratory curiosity to an object of industrial mass production. The main applications of the devices are found...
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Chapter
Laserdioden mit Vertikalresonator (VCSELs) für optische Verbindungssysteme
Laserdioden [1,2] sind ideale Sendeelemente für die faseroptische Kommunikationstechnik. Kantenemittierende Laserdioden werden routinemäßig in der hochbitratigen Langstreckenübertragung bei 1,3 oder 1,55μm Wel...
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Article
GaN Homoepitaxy for Device Applications
Epitaxial growth on GaN single bulk crystals sets new standards in GaN material quality. The outstanding properties provide new insights into fundamental material parameters (e.g. lattice constants, exciton bi...
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Article
Luminescence Related to Stacking Faults in Heterepitaxially Grown Wurtzite GaN
We correlate structure analyzed by transmission electron microscopy with photo- and cathodoluminescence studies of GaN/Al2O3(0001) and GaN/SiC(0001) and show that an additional UV line at 364nm/3.4eV can be conne...
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Article
Determination of the dislocation densities in GaN on c-oriented sapphire
We report on a comprehensive study of the defect structure in GaN grown on c-oriented sapphire by gas source molecular beam epitaxy and metal organic vapour phase epitaxy. Transmission electron microscopy is u...
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Article
Photoluminescence study on GaN homoepitaxial layers grown by molecular beam epitaxy
GaN epitaxial layers on GaN single crystals were grown using molecular beam epitaxy with an NH3 source. The deposited layers were examined by high resolution x-ray diffraction and photoluminescence (PL spectrosco...
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Article
Microstructure, growth mechanisms and electro-optical properties of heteroepitaxial GaN layers on sapphire (0001) substrates
We investigate the structure, growth morphology and the related electro-optical properties of gallium nitride (GaN) films deposited on (0001) sapphire substrates by gas source molecular beam epitaxy (GSMBE) an...
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Article
On Surface Cracking of Ammonia for MBE Growth of GaN
With the use of ammonia as nitrogen precursor for Group III-Nitrides in an on surface cracking (OSC) approach, MBE becomes a serious competitor to MOVPE. Homoepitaxial GaN exhibits record linewidths of 0.5 meV...
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Chapter and Conference Paper
Vertical Cavity Laser Diodes and Arrays for Efficient Fiber Coupling and High Speed Data Transmission in Optical Interconnects
Vertical cavity laser diodes (VCSELs) form a new class of semiconductor lasers extremely prospective for a wide range of applications, e.g. in parallel fiber links, optical interconnects and cross connects, ba...
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Chapter
Physics of Semiconductor Lasers
We are going to study optical processes in semiconductors and semiconductor heterostructures in some detail and describe fundamental properties of classical edge emitting and novel vertical cavity laser diodes...
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Article
NH3 as Nitrogen Source in MBE growth of GaN
We report on the growth of GaN in GSMBE using NH3 as nitrogen source. Special focus will be on the NH3 cracking, where we applied an On Surface Cracking technique (OSC). Using OSC we achieve photoluminescence lin...
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Chapter
Surface Emitting Laser Diodes and Wavelength Break Selective Photodetectors
The structure and fabrication of a vertical cavity surface emitting laser diode is described. The lowest threshold currents are 16mA. The light emission is single longitudinal mode at 915 nm wavelength. Under ...
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Article
Photonic switching in GaAlAs optical strip waveguides by photo-induced electroabsorption
GaAlAs strip waveguides embedded in unbiased pn-junctions are employed for all-optical switching. The underlying physical mechanism is a combination of the photovoltaic effect and the conventional Franz-Keldys...
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Chapter and Conference Paper
Tunable Wavelength Selective Semiconductor Laser Systems
Recently several types of semiconductor lasers have been developed whose emission remains single-longitudinal mode even under gigabit-rate current modulation. Laser diodes with distributed Bragg reflector (DBR...
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Chapter and Conference Paper
Application of High Speed Holocinematographical Methods in Cavitation Research
The dynamics of cavitation bubbles are usually studied by means of high speed cinematographical methods. Several devices like rotating drum, rotating mirror, or image converter cameras are commercially availab...
