Prof. Ferdinand Scholz Profile

Prof. Ferdinand Scholz

at Univ Ulm

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Author

Publications (15)

Proceedings Article | 8 March 2019 Presentation

Growth and optical properties of wurtzite AlBGaN thin films (Conference Presentation)

Ferdinand Scholz, Oliver Rettig, Jan-Patrick Scholz, Natja Steiger, Sebastian Bauer, Yueliang Li, Haoyuan Qi, Johannes Biskupek, Ute Kaiser, Klaus Thonke

Proceedings Volume 10918, 1091802 (2019) https://doi.org/10.1117/12.2506774

KEYWORDS: Boron, Optical properties, Thin films, Luminescence, Light emitting diodes, Active optics, Quantum wells, Crystals, Vapor phase epitaxy, Surface roughness

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Proceedings Article | 14 March 2018 Presentation

GaN-based heterostructures for gas and bio sensing (Conference Presentation)

Ferdinand Scholz, Martin Schneidereit, Florian Huber, Sabyasashi Chakrabortty, Paulette Iskandar, Jassim Shahbaz, Benedikt Hoerbrandt, Tanja Weil, Klaus Thonke

Proceedings Volume 10532, 105321G (2018) https://doi.org/10.1117/12.2286327

KEYWORDS: Quantum wells, Chemical fiber sensors, Sensors, Biosensing, Luminescence, Transducers, Molecules, Nanostructures, Gallium nitride, Biosensors

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Proceedings Article | 8 March 2016 Paper

Development of semipolar (11-22) LEDs on GaN templates

B. Corbett, Z. Quan, D. V. Dinh, G. Kozlowski, D. O'Mahony, M. Akhter, S. Schulz, P. Parbrook, P. Maaskant, M. Caliebe, M. Hocker, K. Thonke, F. Scholz, M. Pristovsek, Y. Han, C. Humphreys, F. Brunner, M. Weyers, T. Meyer, L. Lymperakis

Proceedings Volume 9768, 97681G (2016) https://doi.org/10.1117/12.2204758

KEYWORDS: Light emitting diodes, Gallium nitride, Visible radiation, Sapphire, Chemical mechanical planarization, Surface finishing, Quantum wells, Semiconducting wafers, Polarization, Indium, Indium gallium nitride

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Proceedings Article | 8 March 2014 Paper

Crystal quality improvement of semipolar (20-21) GaN on patterned sapphire substrates by in-situ deposited SiN mask

Tobias Meisch, Maryam Alimoradi-Jazi, Benjamin Neuschl, Martin Klein, Ingo Tischer, Klaus Thonke, Ferdinand Scholz

Proceedings Volume 8986, 89860A (2014) https://doi.org/10.1117/12.2037238

KEYWORDS: Gallium nitride, Crystals, X-rays, Reflection, Patterned sapphire substrate, Temperature metrology, Epitaxy, Sapphire, Scanning electron microscopy, Vapor phase epitaxy

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Proceedings Article | 9 February 2011 Paper

Efficient 350 nm LEDs on low edge threading dislocation density AlGaN buffer layers

Richard Gutt, Thorsten Passow, Wilfried Pletschen, Michael Kunzer, Lutz Kirste, Kamran Forghani, Ferdinand Scholz, Oliver Klein, Ute Kaiser, Klaus Köhler, Joachim Wagner

Proceedings Volume 7954, 79540Q (2011) https://doi.org/10.1117/12.873531

KEYWORDS: Light emitting diodes, Gallium nitride, Electroluminescence, Reflectivity, Crystals, Aluminum, 3D metrology, Atomic force microscopy, External quantum efficiency, Transmission electron microscopy

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Proceedings Article | 28 February 2008 Paper

Optimization of semipolar GaInN/GaN blue/green light emitting diode structures on {1-101} GaN side facets

T. Wunderer, J. Hertkorn, F. Lipski, P. Brückner, M. Feneberg, M. Schirra, K. Thonke, I. Knoke, E. Meissner, A. Chuvilin, U. Kaiser, F. Scholz

Proceedings Volume 6894, 68940V (2008) https://doi.org/10.1117/12.763400

KEYWORDS: Gallium nitride, Light emitting diodes, Luminescence, Indium, Quantum wells, Transmission electron microscopy, Electroluminescence, Atomic force microscopy, Quantum efficiency, Crystals

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Proceedings Article | 16 February 2005 Paper

Red VCSEL for automotive applications

Robert Rossbach, Tabitha Ballmann, Rainer Butendeich, Ferdinand Scholz, Heinz Schweizer, Michael Jetter

Proceedings Volume 5663, (2005) https://doi.org/10.1117/12.597025

KEYWORDS: Vertical cavity surface emitting lasers, Aluminum, Modulation, Gallium, Temperature metrology, Reflectivity, Data modeling, Oxides, Aluminium gallium indium phosphide, Interfaces

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Proceedings Article | 20 December 2004 Paper

Red light VCSEL for high-temperature applications

Michael Jetter, Robert Rossbach, Rainer Butendeich, Ferdinand Scholz, Tabitha Ballmann, Heinz Schweizer

Proceedings Volume 5594, (2004) https://doi.org/10.1117/12.578279

KEYWORDS: Vertical cavity surface emitting lasers, Aluminum, Reflectivity, Mirrors, Gallium, Temperature metrology, Aluminium gallium indium phosphide, Oxides, Resistance, Oxidation

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Proceedings Article | 21 June 2004 Paper

Absorption in InGaN-on-sapphire LED structures: comparison between photocurrent measurement method (PMM) and photothermal deflection spectroscopy (PDS)

Sven Schad, Barbara Neubert, Jens Bruening, Christoph Eichler, Frank Habel, Ferdinand Scholz, Peter Unger, Daniel Hofstetter

Proceedings Volume 5366, (2004) https://doi.org/10.1117/12.528783

KEYWORDS: Absorption, Light emitting diodes, Sapphire, Gallium nitride, Scattering, Waveguides, Spectroscopy, Absorbance, Sensors, Data modeling

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Proceedings Article | 8 December 2003 Paper

Red surface emitters: powerful and fast

Heinz Schweizer, Tabitha Ballmann, Rainer Butendeich, Robert Rossbach, Bernd Raabe, Michael Jetter, Ferdinand Scholz

Proceedings Volume 5248, (2003) https://doi.org/10.1117/12.512626

KEYWORDS: Vertical cavity surface emitting lasers, Modulation, Data communications, Laser applications, Gallium, Indium gallium phosphide, Temperature metrology, Oxides, Aluminum, Quantum wells

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Vertical cavity surface emitting lasers (VCSEL) in the GaInP/AlGaInP material system have experienced a rapid development in their short history. In general lasers from that material system are suitable for a huge number of applications beginning with TV lasers and high power lasers for edge emitters, continuing with optical data storage, medical applications as well as data communication in cars, air planes, offices and between computers as application field for VCSELs. Especially automotive applications show the highest requirements on a laser with respect to operation temperature and power. In this talk we draw out the problems of the material system AlGaInP and its implications for laser applications. We discuss the epitaxial and technological solutions to overcome at least a part of these inherent problems. We will discuss the possible power that we can expect from VCSELs emitting in the range between 650 nm to 670 nm. We got from our lasers 5 mW, CW @ RT, 670nm and 2.5mW, CW@RT, 650 nm. We emphasize the role of doping, Bragg mirror grading, suitable detuning of cavity mode and gain, and optimisation of the contact layer and control of the oxide aperture in the VCSEL structure to get improved operation characteristics at higher temperatures. From the analysis of high frequency measurements, we could evaluate modulation bandwidths between 4 GHz and 10 GHz. The application of polyimide as a dielectric isolation material shows the potential to obtain modulation bandwidths beyond 10 GHz. For the intrinsic modulation bandwidth we get a value of 25 GHz, which is near the value edge emitters show. A more detailed discussion on photon lifetimes and carrier transport times will be given in the talk. Red light emitting VCSELS driven with short current pulses showed laser emission up to + 160°C case temperature. Thus, a CW operation up to +120°C can be expected after further improvement of power generation (decrease of series resistance) and heat spreading (optimized contacts and mounting). From these characteristics we can conclude that AlGaInP-surface emitting lasers have a real potential as low cost lasers for automotive applications as we all as data communication applications up to 10 GHz.

Proceedings Article | 24 June 2002 Paper

Generalized ellipsometry of complex mediums in layered systems

Mathias Schubert, Alexander Kasic, Tino Hofmann, Volker Gottschalch, Juergen Off, Ferdinand Scholz, Eva Schubert, Horst Neumann, Ian Hodgkinson, Matthew Arnold, Wayne Dollase, Craig Herzinger

Proceedings Volume 4806, (2002) https://doi.org/10.1117/12.472993

KEYWORDS: Ellipsometry, Dielectrics, Picosecond phenomena, Data modeling, Crystals, Gallium nitride, Thin films, Phonons, Anisotropy, Gallium

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Proceedings Article | 10 December 2001 Paper

Infrared spectroscopic ellipsometry for nondestructive characterization of free-carrier and crystal-structure properties of group-III-nitride semiconductor device heterostructures

Mathias Schubert, Alexander Kasic, Stephan Figge, Marc Diesselberg, Sven Einfeldt, Detlef Hommel, Ulrich Koehler, Donat As, Juergen Off, Bertram Kuhn, Ferdinand Scholz, John Woollam, Craig Herzinger

Proceedings Volume 4449, (2001) https://doi.org/10.1117/12.450109

KEYWORDS: Gallium nitride, Phonons, Light emitting diodes, Infrared spectroscopy, Stereolithography, Infrared radiation, Gallium, Heterojunctions, Data modeling, Crystals

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Proceedings Article | 6 August 1999 Paper

Optical gain and waveguiding in GaN-based quantum well lasers

S. Heppel, R. Wirth, J. Im, Juergen Off, Ferdinand Scholz, Andreas Hangleiter

Proceedings Volume 3625, (1999) https://doi.org/10.1117/12.356893

KEYWORDS: Quantum wells, Sapphire, Silicon carbide, Polarization, Cladding, Gallium nitride, Semiconductor lasers, Waveguides, Refractive index, Tin

Proceedings Article | 4 December 1998 Paper

Red AlGaInP-lasers: tunable and powerful

Heinz Schweizer, N. Lichtenstein, H. Gauggel, Justus Kuhn, R. Hofmann, R. Winterhoff, Christian Geng, A. Mortiz, Andreas Hangleiter, Ferdinand Scholz

Proceedings Volume 3491, (1998) https://doi.org/10.1117/12.328678

KEYWORDS: Waveguides, Oscillators, Laser damage threshold, Semiconductor lasers, Resonators, Tunable lasers, Optical amplifiers, High power lasers, Reflectivity, Dry etching

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Proceedings Article | 19 June 1995 Paper

Optoelectronic nanostructures: physics and technology

Heinz Schweizer, Uwe Griesinger, Volker Haerle, Frank Adler, Manfred Burkard, Frank Barth, Juergen Hommel, Christiane Kaden, Janos Kovac, Justus Kuhn, Bernd Klepser, Georg Lehr, Freek Prins, Ferdinand Scholz, Manfred Pilkuhn, Josef Straka, Alfred Forchel, Gilbert Smith

Proceedings Volume 2399, (1995) https://doi.org/10.1117/12.212517

KEYWORDS: Laser damage threshold, Etching, Photomasks, Nanostructures, Semiconductors, Laser resonators, Quantum efficiency, Resonators, Ions, Dry etching

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Nanostructures based on III-V semiconductor materials have reached a status which enables basic physical studies on size effects in device and in nanostructures. The expected benefits of high modulation bandwidth, low laser threshold, and improved linewidth enhancement factor in DFB lasers, to say only a few, which are believed to be based mainly on the changed density of states (DOS) function in low dimensions might be counterbalanced by altered carrier energy relaxation and k-space filling in those structures. To investigate systematically size effects and device aspects, a continuous change of structure and active device size is needed from 2D to 0D dimensions. This requirement can be met by high resolution electron beam lithography in conjunction with low damage etch processes and epitaxial overgrowth. In this presentation we discuss the technology and design considerations of lasers with low dimensional active regions as well as DOS effects and device relevant carrier relaxation effects. The technology part will focus especially on low damage etch processes such as RIE- ECR. Nearly damage free structuring processes can be demonstrated. Based on this low damage dry etch process we obtained electrically pumped wire DFB lasers with relatively high output power (up to 6 mW) and operation temperature (60 degrees C). Time resolved optical ps-spectroscopy as well as high excitation spectroscopy on wire and dot nanostructures demonstrate strongly changed k-space filling and carrier relaxation mechanisms in low dimensions and represent a serious limitation of device speed. Results obtained from electrically pumped wire DFB lasers confirm the carrier relaxation and k-space filling effects in device structures which have been observed by optical pump experiments in nanostructures. Despite the band filling effects in low dimensional structures, the wire DFB lasers show clearly the expected feature of gain coupling and enhanced differential gain which might demonstrate the applicability of mesoscopic laser devices in common data communication approaches.

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