Hans-Jürgen Lugauer
Osram Opto Semiconductors GmbH
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Publication
Featured researches published by Hans-Jürgen Lugauer.
Applied Physics Express | 2013
Bastian Galler; Hans-Jürgen Lugauer; Michael Binder; Richard Hollweck; Yannick Folwill; Anna Nirschl; Alvaro Gomez-Iglesias; Berthold Hahn; J. Wagner; Matthias Sabathil
We investigate theoretically the influence of type and density of background carriers in the active region on the quantum efficiency of InGaN-based light emitters using an extension of the ABC rate model. A method to determine experimentally whether a certain type of Auger recombination is relevant in InGaN quantum wells is derived from these considerations. Using this approach, we show that the physical process which is the dominant cause for the efficiency droop is superlinear in the electron density and can thus be assigned to nnp-Auger recombination.
Applied Physics Letters | 2016
Felix Nippert; S. Karpov; Gordon Callsen; Bastian Galler; Thomas Kure; Christian Nenstiel; M. R. Wagner; Martin Straßburg; Hans-Jürgen Lugauer; A. Hoffmann
We obtain temperature-dependent recombination coefficients by measuring the quantum efficiency and differential carrier lifetimes in the state-of-the-art InGaN light-emitting diodes. This allows us to gain insight into the physical processes limiting the quantum efficiency of such devices. In the green spectral range, the efficiency deteriorates, which we assign to a combination of diminishing electron-hole wave function overlap and enhanced Auger processes, while a significant reduction in material quality with increased In content can be precluded. Here, we analyze and quantify the entire balance of all loss mechanisms and highlight the particular role of hole localization.
Applied Physics Letters | 2014
M. Auf der Maur; Bastian Galler; I. Pietzonka; Martin Strassburg; Hans-Jürgen Lugauer; A. Di Carlo
Based on numerical simulation and comparison with measured current characteristics, we show that the current in InGaN/GaN single-quantum-well light-emitting diodes at low forward bias can be accurately described by a standard trap-assisted tunneling model. The qualitative and quantitative differences in the current characteristics of devices with different emission wavelengths are demonstrated to be correlated in a physically consistent way with the tunneling model parameters.
Japanese Journal of Applied Physics | 2016
Felix Nippert; S. Karpov; Ines Pietzonka; Bastian Galler; Alexander Wilm; Thomas Kure; Christian Nenstiel; Gordon Callsen; Martin Straßburg; Hans-Jürgen Lugauer; A. Hoffmann
We suggest a novel technique for the evaluation of the recombination coefficients corresponding to Shockley–Read–Hall, radiative, and Auger recombination that occur in InGaN/GaN-based light-emitting diodes (LEDs). This technique combines the measurement of the LED efficiency as a function of LED drive current with a small-signal time-resolved photoluminescence measurement of the differential carrier life time (DLT). Using the relationships between the efficiency and DLT following from the empirical ABC-model, one can evaluate all three recombination coefficients. The suggested technique is applied to a number of single- and multiple-quantum well LEDs to gain a deeper insight into the mechanisms ultimately limiting their efficiency.
Applied Physics Letters | 2014
Holger Koch; F. Bertram; Ines Pietzonka; Jan-Philipp Ahl; Martin Strassburg; Olga August; J. Christen; H. Kalisch; Andrei Vescan; Hans-Jürgen Lugauer
A comprehensive study on the impact of growth modes on the structural and optical properties of thick InGaN layers suitable for photovoltaic application is presented. Samples grown by metalorganic vapour phase epitaxy with different growth rates and thicknesses have been analyzed. The application of slow growth rates result in smooth layers while higher growth rates induce a meandering surface morphology. Using low-temperature cathodoluminescence, a direct correlation of the morphology to local luminescent properties is obtained: the top of meandering structures reveals a spectrally red-shifted emission compared to the emission wavelength expected from the average indium content determined by X-ray diffraction. The origin of this shift is identified and explained by increased indium incorporation on top of the meander due to a spatially localized compositional pulling effect.
Semiconductor Science and Technology | 1996
J Kraus; E. Kurtz; S. Einfeldt; D. Hommel; Hans-Jürgen Lugauer; A. Waag
We have investigated the Raman signals of vibrational modes and the phonon sidebands of resonantly excited donor - acceptor-pair recombination in p-doped CdTe and ZnSe. Under resonant excitation of donor - acceptor-pair states we observe an enhanced sensitivity of the optical spectroscopy to the spectrum of local vibrational excitations. The measured signals are interpreted as local vibrational modes of the dopants or as phonons with wavevectors at distinguished points of the Brillouin zone others than the centre point . These latter signals correspond either to the maxima of the phonon density of states of the host crystal or to longitudinal optical phonons with finite but discrete wavevectors defined by the donor - acceptor-pair separations. The results can contribute to the characterization of the materials as well as to the investigation of the processes of the acceptor compensation.
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXII | 2018
S. Karpov; Bastian Galler; Thomas Kure; M. R. Wagner; Hans-Jürgen Lugauer; Martin Strassburg; Axel Hoffmann; Gordon Callsen; Felix Nippert
We review recent advances in the understanding of the green gap phenomenon, the drastic reduction of quantum efficiency of c-plane InGaN/GaN light-emitting diodes (LEDs) towards the green spectral region. In particular, we have decoupled the contributions of Shockley-Read-Hall recombination, quantum-confined Stark effect and hole localization in the random alloy. We show that the latter, significantly increasing with Indium content, plays a crucial role in the reduction of efficiency, as localized holes do not only possess lower overlap with delocalized electrons in the quantum well, but also appear to enhance Auger recombination. For our study we use an electro-optical pump and probe scheme[1], which is most suitable to obtain differential carrier lifetimes in device operating conditions. In combination with conventional pulsed electroluminescence measurements, the internal quantum efficiency and recombination rates of the different processes can be determined. Temperature-dependent analyses then allow to assign recombination losses to the different underlying limitations (i.e. random alloying, polarity, defect density)[2]. [1] F. Nippert et al., Japanese Journal of Applied Physics 55, 05FJ01 (2016) [2] F. Nippert et al., Applied Physics Letters 109, 161103 (2016)
Applied Physics Letters | 2018
Felix Nippert; Mohammad Tollabi Mazraehno; Matthew J. Davies; Marc P. Hoffmann; Hans-Jürgen Lugauer; Thomas Kure; Michael Kneissl; A. Hoffmann; M. R. Wagner
We show that the often observed efficiency droop in AlGaN quantum well heterostructures is an internal carrier loss process, analogous to the InGaN system. We attribute this loss process to Auger recombination, with C = 2.3 × 10−30 cm6 s−1; a similar value found commonly in InGaN-based devices. As a result, the peak internal quantum efficiency (IQE) of our structures is limited to 66%. These values were obtained by resonant excitation (time-resolved) photoluminescence (PL), avoiding common error sources in IQE measurements. The existence of strong Auger recombination implies that simple methods employed for IQE determination, such as temperature-dependent PL, may lead to erroneous values. Auger losses will have to be considered once the challenges regarding carrier injection are solved.We show that the often observed efficiency droop in AlGaN quantum well heterostructures is an internal carrier loss process, analogous to the InGaN system. We attribute this loss process to Auger recombination, with C = 2.3 × 10−30 cm6 s−1; a similar value found commonly in InGaN-based devices. As a result, the peak internal quantum efficiency (IQE) of our structures is limited to 66%. These values were obtained by resonant excitation (time-resolved) photoluminescence (PL), avoiding common error sources in IQE measurements. The existence of strong Auger recombination implies that simple methods employed for IQE determination, such as temperature-dependent PL, may lead to erroneous values. Auger losses will have to be considered once the challenges regarding carrier injection are solved.
Archive | 2004
Volker Härle; Berthold Hahn; Hans-Jürgen Lugauer; Helmut Bolay; Stefan Bader; Dominik Eisert; Uwe Strauss; Johannes Völkl; Ulrich Zehnder; Alfred Lell; Andreas Weimer
Archive | 2004
Volker Härle; Berthold Hahn; Hans-Jürgen Lugauer