21 results on '"Roland Zeisel"'
Search Results
2. Monolithic integrable capacitive humidity sensing method for material characterization of dielectric thin films.
- Author
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Andreas Rückerl, Sophia Huppmann, Roland Zeisel, and Simeon Katz
- Published
- 2014
- Full Text
- View/download PDF
3. Correlation of Optical, Structural, and Compositional Properties with V-Pit Distribution in InGaN/GaN Multiquantum Wells
- Author
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Roland Zeisel, Marvin Hartwig Zoellner, C. L. Manganelli, Thomas Schroeder, Ulrich Theodor Schwarz, Tobias U. Schülli, Lise Lahourcade, Gilbert André Chahine, and Christian Mounir
- Subjects
010302 applied physics ,Diffraction ,Materials science ,Photoluminescence ,business.industry ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,law ,0103 physical sciences ,Microscopy ,Sapphire ,Optoelectronics ,General Materials Science ,Grain boundary ,0210 nano-technology ,business ,Microscale chemistry ,Light-emitting diode - Abstract
InGaN/GaN double heterostructures and multiquantum wells (MQWs) have been successfully developed since more than 20 years for LED lightning applications. Recent developments show that state-of-the-art LEDs benefit from artificially generated V-pit defects. However, the control of structural and chemical properties plays a tremendous role. In this paper, we report on the lateral distribution of V-pit defects and photoluminescence of InGaN/GaN MQWs grown on thick GaN on patterned sapphire substrates. The synchrotron-based scanning X-ray diffraction microscopy technique K-map was employed to locally correlate these properties with the local tilt, strain, and composition of the InGaN/GaN MQW. Compositional fluctuation is the main factor for the variation of photoluminescence intensity and broadening. In turn, V-pit defects align along small-angle grain boundaries and their strain fields are identified as a reason for promoting the InGaN segregation process on a microscale.
- Published
- 2019
4. Evidence for avalanche generation in reverse-biased InGaN LEDs
- Author
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Gaudenzio Meneghesso, Pradip Dalapati, Roland Zeisel, Bastian Galler, C. De Santi, Enrico Zanoni, Nicola Renso, Desiree Monti, Matteo Meneghini, and Michael Binder
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Avalanche-generation ,Range (particle radiation) ,Materials science ,Photoluminescence ,Photon ,business.industry ,LED ,Electron ,Electroluminescence ,GaN ,Reverse-bias ,law.invention ,law ,High-electric-field ,Optoelectronics ,business ,Quantum tunnelling ,Excitation ,Light-emitting diode - Abstract
Avalanche generation is a physical mechanism responsible for the breakdown at extremely high field, such as in the reverse bias conditions typical of ESD discharges. In this work, for the first time we provide experimental evidence that avalanche generation can take place in state-of-the-art InGaN-based blue LEDs. We measured the current-voltage and electroluminescence curves of the devices while pulsing them with increasing reverse voltages. We investigated a wide span of temperatures (from cryogenic to room temperature) in order to verify that the increase in leakage current detected below -80 V is related to avalanche generation (positive temperature-coefficient). Numerical simulations show that in this bias condition the band-to-band tunneling barrier thickness is low, leading to the possible injection of highly-energetic electrons from the p-side to the n-side that can start the avalanche process. The spectral shape shows a broad emission, covering the spectral range between 1.25 and 3.5 eV; the low energy side slowly decreases below 2.2 eV, and two sharp edges are seen at the high-energy side. Since an avalanche generation process is present, we can interpret the spectrum as follows: (i) hole and electron pairs generated by the avalanche process recombine, emitting photons; (ii) high-energy side: reabsorption of the emitted photons in the In-containing layers and nGaN side, confirmed by the red-shift at higher temperature; (iii) low-energy side: internal photoluminescence of the defects in the n-GaN layer, confirmed by PL measurements with external excitation. A theoretical computation based on this model is able to reproduce the experimental data.
- Published
- 2019
5. Influence of the Growth Substrate on the Internal Quantum Efficiency of AlGaN/AlN Multiple Quantum Wells Governed by Carrier Localization
- Author
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Christian Frankerl, Hans-Jürgen Lugauer, Nadine Tillner, Axel Hoffmann, Gwénolé Jacopin, Roland Zeisel, Georg Rossbach, Matthew J. Davies, Christian Brandl, Marc Patrick Hoffmann, Semi-conducteurs à large bande interdite (SC2G), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), and Technische Universität Berlin (TU)
- Subjects
010302 applied physics ,Materials science ,Photoluminescence ,business.industry ,Cathodoluminescence ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Crystallographic defect ,Electronic, Optical and Magnetic Materials ,law.invention ,[SPI]Engineering Sciences [physics] ,law ,0103 physical sciences ,Sapphire ,Optoelectronics ,Quantum efficiency ,Metalorganic vapour phase epitaxy ,0210 nano-technology ,business ,Light-emitting diode - Abstract
International audience; The influence of the growth substrate on the internal quantum efficiency (IQE) of deep ultraviolet (UV) light emitting diodes is studied. Two nominally identical Al-rich AlGaN/AlN multi-quantum-well (MQW) structures grown by metalorganic vapour phase epitaxy (MOVPE) on different substrates were investigated. The first MQW structure was grown on a native AlN substrate, while the second one was deposited on an AlN template on sapphire. By the combination of atomic force microscopy (AFM), photoluminescence (PL) and cathodoluminescence (CL) spectroscopy, we demonstrate that the dislocation-mediated spiral growth of MQWs on sapphire results in the more efficient localization of carriers. This effect helps to prevent non-radiative carrier recombination at point defects, improving the IQE of the structure. I.
- Published
- 2020
6. Origin of carrier localization in AlGaN-based quantum well structures and implications for efficiency droop
- Author
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Roland Zeisel, Hans-Jürgen Lugauer, Matthew J. Davies, Christian Brandl, Marc Patrick Hoffmann, Alvaro Gomez-Iglesias, Axel Hoffmann, Felix Nippert, and Christian Frankerl
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010302 applied physics ,Photoluminescence ,Materials science ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Auger effect ,Oscillator strength ,Exciton ,02 engineering and technology ,Electron ,Photon energy ,021001 nanoscience & nanotechnology ,01 natural sciences ,symbols.namesake ,0103 physical sciences ,symbols ,Voltage droop ,0210 nano-technology ,Quantum well - Abstract
We investigate carrier localization in Al-rich AlGaN/AlN quantum well (QW) structures. Low temperature time-resolved photoluminescence (PL) experiments reveal a strong variation of the carrier decay times with detection photon energy, suggesting a strong impact of carrier localization, which is found to depend primarily on the QW width. In combination with time-integrated PL measurements and numerical band structure calculations, we are able to provide conclusive evidence that the localization strength in AlGaN-based QW structures is directly coupled to the oscillator strength, providing an explanation for its strong dependence on the QW width. This is further supported by the observation of a strong polarization field dependency of the carrier localization, which excludes excitons and may be explained by the accumulation of electrons close to the QW interface, while holes are independently localized across the QW. We complete our discussion by proposing a model to explain the well-known phenomenon of efficiency droop in accordance with our findings, suggesting delocalization-induced Auger recombination as the responsible loss channel.
- Published
- 2020
7. Point Defect‐Induced UV‐C Absorption in Aluminum Nitride Epitaxial Layers Grown on Sapphire Substrates by Metal‐Organic Chemical Vapor Deposition
- Author
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Roland Zeisel, Rainer Lösing, Hans-Jürgen Lugauer, Axel Hoffmann, Andreas Waag, Felix Nippert, Christian Brandl, Matthew J. Davies, Marc Patrick Hoffmann, Martin Mandl, Nadine Tillner, and Christian Frankerl
- Subjects
Materials science ,Photoluminescence ,Absorption spectroscopy ,Analytical chemistry ,Photoluminescence excitation ,Metalorganic vapour phase epitaxy ,Chemical vapor deposition ,Nitride ,Condensed Matter Physics ,Epitaxy ,Absorption (electromagnetic radiation) ,Electronic, Optical and Magnetic Materials - Abstract
Herein, the optical properties of aluminum nitride (AlN) epitaxial layers grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) are reported. The structures investigated in this study are grown at highly different degrees of supersaturation in the MOCVD process. In addition, both pulsed and continuous growth conditions are employed and AlN is deposited on nucleation layers favoring different polarities. The samples are investigated by photoluminescence (PL), photoluminescence excitation (PLE), and absorption spectroscopy and are found to vary significantly in absorption and emission characteristics. Two distinct absorption bands in the UV-C spectral range are observed and examined in greater detail, with either giving rise to a significant absorption coefficient of around 1000 cm−1. The corresponding defect transitions are identified by PL spectroscopy. Combined with secondary-ion mass spectrometry (SIMS) measurements, these absorption bands are allocated to the incorporation of carbon and oxygen impurities, depending on the applied growth conditions. Furthermore, similarities with other epitaxial growth techniques serving as basis for UV-C applications are highlighted. These results are highly relevant for a better understanding of absorption issues in AlN templates grown by various deposition techniques. In addition, consequences for the growth of efficient UV-C devices by MOCVD on sapphire substrates are outlined.
- Published
- 2020
8. Carrier Dynamics in Al‐Rich AlGaN/AlN Quantum Well Structures Governed by Carrier Localization
- Author
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Matthew J. Davies, Christian Brandl, Marc Patrick Hoffmann, Axel Hoffmann, Hans-Jürgen Lugauer, Felix Nippert, Christian Frankerl, and Roland Zeisel
- Subjects
Materials science ,Photoluminescence ,Thermal ,Voltage droop ,Emission spectrum ,Photon energy ,Condensed Matter Physics ,Molecular physics ,Recombination ,Excitation ,Quantum well ,Electronic, Optical and Magnetic Materials - Abstract
The carrier dynamics of Al-rich AlGaN/AlN quantum well (QW) structures in the presence of strong carrier localization is reported. Excitation density-dependent photoluminescence (PL) measurements at low temperatures reveal a clear correlation between the onset of efficiency droop and the broadening of the time-integrated PL spectra. While the droop onset is heavily impacted by the localization strength, the PL emission broadening is observed almost exclusively on the high energy side of the emission spectrum. Spectrally resolved PL decay transient measurements reveal a strong dependency of the carrier lifetimes on the emission photon energy across the spectrum, consistent with a distribution of localized states, as well as on the temperature, depending on the localization strength of the investigated structure. The characteristic “S”-shaped temperature dependence of the PL emission energy is shown to be directly correlated to the thermal redistribution of carriers between localized states. Based on these findings, the role of carrier localization in the recombination processes in AlGaN QW structures is underlined and its implications for efficiency droop are discussed.
- Published
- 2020
9. Strongly localized carriers in Al-rich AlGaN/AlN single quantum wells grown on sapphire substrates
- Author
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Matthew J. Davies, Hans-Jürgen Lugauer, Christian Frankerl, Christian Brandl, Marc Patrick Hoffmann, Heng Wang, Axel Hoffmann, Felix Nippert, and Roland Zeisel
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010302 applied physics ,Range (particle radiation) ,Photoluminescence ,Materials science ,business.industry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,01 natural sciences ,chemistry ,Aluminium ,0103 physical sciences ,Sapphire ,Optoelectronics ,Quantum efficiency ,0210 nano-technology ,business ,Spectroscopy ,Quantum well - Abstract
Carrier dynamics in AlGaN-based single quantum well (QW) structures grown on sapphire are studied by means of time-integrated and time-resolved photoluminescence spectroscopy (PL) in a wide temperature range from 5 K to 350 K. The samples cover a broad compositional range, with aluminum contents ranging between 42% and 60% and QW widths between 1.5 nm and 2.5 nm. All samples reveal the characteristic “S”-shape temperature dependence of the PL emission energy as frequently reported in InGaN-based systems, albeit with significantly larger localization strengths of up to 60 meV. It is shown that in the compositional range investigated, carrier localization is determined primarily by the QW width and, in contrast, exhibits a much weaker dependence on aluminum concentration. By the combination of time-integrated and time-resolved PL measurements, the localization of carriers is demonstrated to have a significant impact on the recombination dynamics of AlGaN/AlN QWs grown on sapphire, heavily affecting the internal quantum efficiency and efficiency droop even in standard LED operation conditions.
- Published
- 2020
10. Challenges for reliable internal quantum efficiency determination in AlGaN-based multi-quantum-well structures posed by carrier transport effects and morphology issues
- Author
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Matthew J. Davies, Felix Nippert, Axel Hoffmann, Hans-Jürgen Lugauer, Christian Frankerl, Roland Zeisel, Christian Brandl, Marc Patrick Hoffmann, Nadine Tillner, and Heng Wang
- Subjects
010302 applied physics ,Materials science ,Photoluminescence ,business.industry ,Optical measurements ,Wide-bandgap semiconductor ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Resonance (particle physics) ,0103 physical sciences ,Optoelectronics ,Quantum efficiency ,0210 nano-technology ,business ,Spectroscopy ,Excitation ,Quantum well - Abstract
We report on a systematic study of the determination of the internal quantum efficiency (IQE) in AlGaN-based multiple-quantum-well (MQW) structures using different optical evaluation methodologies and experimental conditions, in order to derive a standard set of measurement conditions for reliable IQE determination. Several potential sources of error that may distort the IQE obtained by optical measurements are discussed, such as carrier transport effects, excitation conditions failing to fulfill ideal resonance conditions, and morphology issues. A series of nominally identical AlGaN-based MQW structures is grown on an AlGaN layer separated by an AlN interlayer of varying thickness. The MQW structures are studied both by resonant and quasiresonant photoluminescence spectroscopy, and IQEs are determined via different commonly employed methods. The obtained values are shown to be significantly affected by the employed excitation conditions, as well as the evaluation techniques. In addition, growth morphology issues and carrier transport effects need to be considered in the interpretation of the measured data, with the latter being investigated in greater detail. The results emphasize the need for an appropriate choice of both experimental conditions and evaluation methodology in order to extract reliable and comparable IQE values.
- Published
- 2019
11. Towards quantification of the crucial Impact of auger recombination for the Efficiency droop in (AlInGa)N Quantum well structures
- Author
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Michael Binder, Hans-Jürgen Lugauer, Ines Pietzonka, Bastian Galler, Dominique Bougeard, Anna Nirschl, Roland Zeisel, Marina Schmid, and Matthias Sabathil
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010302 applied physics ,Physics ,Photoluminescence ,Auger effect ,ddc:530 ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,530 Physik ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,3. Good health ,law.invention ,Auger ,symbols.namesake ,law ,0103 physical sciences ,symbols ,Quantum efficiency ,Voltage droop ,Atomic physics ,0210 nano-technology ,Quantum well ,Light-emitting diode - Abstract
Recent experimental investigations on the reduction of internal quantum efficiency with increasing current density in (AlInGa)N quantum well structures show that Auger recombination is a significant contributor to the so-called "droop" phenomenon. Using photoluminescence (PL) test structures, we find Auger processes are responsible for at least 15 % of the measured efficiency droop. Furthermore, we confirm that electron-electron-hole (nnp) is stronger than electron-hole-hole (npp) Auger recombination in standard LEDs. The ratio of respective Auger coefficients is determined to be in the range 1 < C-nnp = C-npp
- Published
- 2016
12. Thermal droop in InGaN-based LEDs: physical origin and dependence on material properties
- Author
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Stefano Dominici, Gaudenzio Meneghesso, M. Mandurrino, Roland Zeisel, Enrico Zanoni, C. De Santi, Francesco Bertazzi, Bastian Galler, Michele Goano, Nicola Trivellin, Matteo Meneghini, M. La Grassa, and Berthold Hahn
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Materials science ,Phonon ,Thermionic emission ,Gallium nitride ,02 engineering and technology ,Electron blocking layer ,Light emitting diode ,Indium gallium nitride ,01 natural sciences ,Thermal droop ,chemistry.chemical_compound ,0103 physical sciences ,Voltage droop ,Carrier escape ,Shockley-Read-Hall recombination ,Quantum well ,Quantum tunnelling ,Diode ,010302 applied physics ,business.industry ,021001 nanoscience & nanotechnology ,chemistry ,Optoelectronics ,0210 nano-technology ,business - Abstract
The thermal droop (reduction of the optical power when the temperature is increased) is a phenomenon that strongly limits the efficiency of InGaN-based light-emitting diodes. In this paper we analyze the role of Shockley-Read-Hall (SRH) recombination and of the electron blocking layer (EBL) in the process by using numerical simulations and literature data. The benefic impact of EBL suggests that carrier escape from the quantum wells gives a significant contribution to the thermal droop, therefore we review some of the mechanisms described in the literature (thermionic emission, phonon-assisted tunneling, thermionic trap-assisted tunneling). Since no formulation is able to fit the behavior of the measured SQW devices, we develop a new model based on two phonon-assisted tunneling steps through a defective state, extended in order to take into account zero-field emission. By using experimental data, material constants from the literature and only two fitting parameters the model is able to reproduce the experimental behavior.
- Published
- 2016
13. Role of defects in the thermal droop of InGaN-based light emitting diodes
- Author
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Bastian Galler, Michele Goano, Roland Zeisel, Dipika Robidas, Francesco Bertazzi, M. Mandurrino, Enrico Zanoni, Stefano Dominici, Matteo Meneghini, Gaudenzio Meneghesso, C. De Santi, and M. La Grassa
- Subjects
010302 applied physics ,Materials science ,Condensed matter physics ,Phonon ,business.industry ,Wide-bandgap semiconductor ,General Physics and Astronomy ,Optical power ,Thermionic emission ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Physics and Astronomy (all) ,0103 physical sciences ,Optoelectronics ,Voltage droop ,0210 nano-technology ,business ,Quantum well ,Quantum tunnelling ,Diode - Abstract
This paper reports an investigation of the physical origin of the thermal droop (the drop of the optical power at high temperatures) in InGaN-based light-emitting diodes. We critically investigate the role of various mechanisms including Shockley-Read-Hall recombination, thermionic escape from the quantum well, phonon-assisted tunneling, and thermionic trap-assisted tunneling; in addition, to explain the thermal droop, we propose a closed-form model which is able to accurately fit the experimental data by using values extracted from measurements and simulations and a limited set of fitting parameters. The model is based on a two-step phonon-assisted tunneling over an intermediate defective state, corrected in order to take into account the pure thermionic component at zero bias and the field-assisted term.
- Published
- 2016
14. Ageing of InGaN-based LEDs: Effects on internal quantum efficiency and role of defects
- Author
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M. Mandurrino, Bastian Galler, Marco La Grassa, Carlo De Santi, Roland Zeisel, Michele Goano, Francesco Bertazzi, Matteo Meneghini, Enrico Zanoni, and Gaudenzio Meneghesso
- Subjects
Materials science ,Photoluminescence ,Optical power ,Activation energy ,Efficiency ,Electroluminescence ,law.invention ,Stress (mechanics) ,law ,Light-emitting-diode ,Electrical and Electronic Engineering ,Safety, Risk, Reliability and Quality ,InGaN ,business.industry ,LED ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ageing ,Defects ,Optoelectronics ,Degradation (geology) ,Quantum efficiency ,business ,Light-emitting diode - Abstract
This paper describes the degradation of InGaN-based LEDs submitted to constant current stress; based on combined electroluminescence, photoluminescence and deep-level transient spectroscopy we show that: (i) when submitted to constant current stress, LEDs can show a measurable decrease in the optical power, which is more prominent in the low current regime; (ii) the decrease in optical power is strongly correlated to the increase in the Shockley–Read–Hall recombination coefficient A, as estimated by differential lifetime measurements; (iii) stress induces the increase in the concentration of a trap level, with activation energy between 0.6 and 0.7 eV, which is supposed to be located next to/within the active region. The results suggest that the optical degradation can be ascribed to the increase in non-radiative recombination, rather than to a decrease in carrier injection efficiency.
- Published
- 2015
15. Characterization and prevention of humidity related degradation of atomic layer deposited Al2O3
- Author
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Roland Zeisel, Marvin Hartwig Zoellner, Ioan Costina, Martin Mandl, Thomas Schroeder, and Andreas Rückerl
- Subjects
Boehmite ,Materials science ,Silicon ,Analytical chemistry ,General Physics and Astronomy ,Humidity ,chemistry.chemical_element ,02 engineering and technology ,Dielectric ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry ,Chemical engineering ,Degradation (geology) ,0210 nano-technology ,Silicon oxide ,Layer (electronics) ,Molecular beam epitaxy - Abstract
Atomic layer deposited aluminum oxide (ALD-Al2O3) is a dielectric material, which is widely used in organic light emitting diodes in order to prevent their organic layers from humidity related degradation. Unfortunately, there are strong hints that in some cases, ALD-Al2O3 itself is suffering from humidity related degradation. Especially, high temperature and high humidity seem to enhance ALD-Al2O3 degradation strongly. For this reason, the degradation behavior of ALD-Al2O3 films at high temperature and high humidity was investigated in detail and a way to prevent it from degradation was searched. The degradation behavior is analyzed in the first part of this paper. Using infrared absorbance measurements and X-ray diffraction, boehmite (γ-AlOOH) was identified as a degradation product. In the second part of the paper, it is shown that ALD-Al2O3 films can be effectively protected from degradation using a silicon oxide capping. The deposition of very small amounts of silicon in a molecular beam epitaxy syst...
- Published
- 2017
16. Analysis and in situ observation of humidity dependent atomic layer deposited-Al2O3 degradation
- Author
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Roland Zeisel, Andreas Rückerl, Sophia Huppmann, Simeon Katz, and Martin Mandl
- Subjects
010302 applied physics ,Materials science ,Process Chemistry and Technology ,Analytical chemistry ,chemistry.chemical_element ,Humidity ,02 engineering and technology ,Dielectric ,Penetration (firestop) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Capacitance ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Atomic layer deposition ,chemistry ,Aluminium ,0103 physical sciences ,Materials Chemistry ,Hydroxide ,Wetting ,Electrical and Electronic Engineering ,0210 nano-technology ,Instrumentation - Abstract
The degradation of atomic layer deposited aluminum oxide (ALD-Al2O3) at high temperature and high humidity was investigated. The intrinsic hydroxyl concentration of as-deposited ALD-Al2O3 was evaluated using a temperature dependent deposition study and its impact on degradation behavior was analyzed. In addition, the degradation of ALD-Al2O3 was monitored in situ using a plate capacitor with ALD-Al2O3 as dielectric. A model for the ALD-Al2O3 degradation mechanism was proposed based on the penetration of water molecules into the ALD-Al2O3 and on the formation of aluminum hydroxide. Two parameters, delay-time (time till a change in capacitance occurs) and wetting speed (speed of molecular water penetration into the ALD-Al2O3), were extracted from the capacitance measurements in order to evaluate the dependence of ALD-Al2O3 degradation on temperature and humidity.
- Published
- 2017
17. Characterization of the deep levels responsible for non-radiative recombination in InGaN/GaN light-emitting diodes
- Author
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Berthold Hahn, Bastian Galler, Enrico Zanoni, P. Drechsel, Gaudenzio Meneghesso, M. La Grassa, Matteo Meneghini, Roland Zeisel, and S. Vaccari
- Subjects
Materials science ,Deep-level transient spectroscopy ,Physics and Astronomy (miscellaneous) ,business.industry ,Gallium Nitride ,light emitting diodes ,degradation ,Reliability ,Wide-bandgap semiconductor ,Gallium nitride ,Activation energy ,Arrhenius plot ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Optoelectronics ,business ,Light-emitting diode ,Non-radiative recombination ,Diode - Abstract
This paper presents an extensive investigation of the deep levels related to non-radiative recombination in InGaN/GaN light-emitting diodes (LEDs). The study is based on combined optical and deep-level transient spectroscopy measurements, carried out on LEDs with identical structure and with different values of the non-radiative recombination coefficient. Experimental data lead to the following, relevant, results: (i) LEDs with a high non-radiative recombination coefficient have a higher concentration of a trap (labeled as “e2”) with an activation energy of 0.7 eV, which is supposed to be located close to/within the active region; (ii) measurements carried out with varying filling pulse duration suggest that this deep level behaves as a point-defect/dislocation complex. The Arrhenius plot of this deep level is critically compared with the previous literature reports, to identify its physical origin.
- Published
- 2014
18. Identification of nnp and npp Auger recombination as significant contributor to the efficiency droop in (GaIn)N quantum wells by visualization of hot carriers in photoluminescence
- Author
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Bastian Galler, Thomas Hager, Manfred Binder, Dominique Bougeard, Hans-Juergen Lugauer, Roland Zeisel, Matthias Sabathil, Anna Nirschl, Joachim Wagner, and Publica
- Subjects
Photoluminescence ,Physics and Astronomy (miscellaneous) ,Auger effect ,Laser diode ,business.industry ,Chemistry ,ddc:530 ,530 Physik ,Auger ,law.invention ,symbols.namesake ,law ,symbols ,aluminium compounds, Auger effect, carrier density, electron-hole recombination, excited states, gallium compounds, hot carriers, III-V semiconductors, indium compounds, optical pumping, photoluminescence, semiconductor quantum wells, wide band gap semiconductors ,Optoelectronics ,Charge carrier ,Voltage droop ,business ,Quantum well ,Diode - Abstract
We report the direct observation of hot carriers generated by Auger recombination via photoluminescence spectroscopy on tailored (AlGaIn)N multiple quantum well (QW) structures containing alternating green and ultra-violet (UV) emitting (GaIn)N QWs. Optically pumping solely the green QWs using a blue emitting high power laser diode, carrier densities similar to electrical light-emitting diode (LED) operation were achieved, circumventing possible leakage and injection effects. This way, luminescence from the UV QWs could be observed for excitation where the emission from the green QWs showed significant droop, giving direct evidence for Auger generated hot electrons and holes being injected into the UV QWs. An examination of the quantitative relation between the intensity of the UV luminescence and the amount of charge carriers lost due to drooping of the QWs supports the conclusion that Auger processes contribute significantly to the droop phenomenon in (AlGaIn)N based light-emitting diodes.
- Published
- 2013
19. Transport and capture properties of Auger-generated high-energy carriers in (AlInGa)N quantum well structures
- Author
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Ines Pietzonka, Michael Binder, Bastian Galler, M. M. Karow, Roland Zeisel, Dominique Bougeard, Maximilian Schmid, Anna Nirschl, Matthias Sabathil, and Hans-Juergen Lugauer
- Subjects
Photoluminescence ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,Asymmetry ,Auger ,law.invention ,symbols.namesake ,law ,0103 physical sciences ,Quantum well ,media_common ,010302 applied physics ,Auger effect ,Chemistry ,ddc:530 ,Wide-bandgap semiconductor ,530 Physik ,021001 nanoscience & nanotechnology ,symbols ,Quantum efficiency ,Atomic physics ,0210 nano-technology ,Light-emitting diode - Abstract
Recent photoluminescence experiments presented by M. Binder et al. [Appl. Phys. Lett. 103, 071108 (2013)] demonstrated the visualization of high-energy carriers generated by Auger recombination in (AlInGa)N multi quantum wells. Two fundamental limitations were deduced which reduce the detection efficiency of Auger processes contributing to the reduction in internal quantum efficiency: the transfer probability of these hot electrons and holes in a detection well and the asymmetry in type of Auger recombination. We investigate the transport and capture properties of these high-energy carriers regarding polarization fields, the transfer distance to the generating well, and the number of detection wells. All three factors are shown to have a noticeable impact on the detection of these hot particles. Furthermore, the investigations support the finding that electron-electron-hole exceeds electron-hole-hole Auger recombination if the densities of both carrier types are similar. Overall, the results add to the evidence that Auger processes play an important role in the reduction of efficiency in (AlInGa)N based LEDs.
- Published
- 2015
20. Investigations on correlation between I–V characteristic and internal quantum efficiency of blue (AlGaIn)N light-emitting diodes
- Author
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Bastian Galler, M. Furitsch, Michael Binder, Joachim Wagner, Roland Zeisel, Jürgen Off, and S. Katz
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Orders of magnitude (temperature) ,Wide-bandgap semiconductor ,chemistry.chemical_element ,law.invention ,Semiconductor ,chemistry ,law ,Optoelectronics ,Quantum efficiency ,business ,Platinum ,Current density ,Light-emitting diode ,Diode - Abstract
We have studied the electrical and optical characteristics of (AlGaIn)N multiple quantum well light-emitting diodes. Minimizing contact effects by utilizing platinum as p-contact metal, ideality factors as low as 1.1 have been achieved. In agreement with basic semiconductor theory, a correlation between ideality factor and small-current efficiency was found. We were able to emulate the experimental current-voltage characteristic over seven orders of magnitude utilizing a two diode model. This model enables a very good prediction of internal quantum efficiency at moderate current densities out of purely electrically derived parameters.
- Published
- 2013
21. Carrier transport in green AlInGaN based structures on c-plane substrates
- Author
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T. Wurm, Roland Zeisel, Bastian Galler, Christoph Eichler, S. Gerhard, Georg Brüderl, Michael Binder, Thomas Hager, Uwe Strauss, Alvaro Gomez-Iglesias, Adrian Stefan Avramescu, Sönke Tautz, and Bernhard Stojetz
- Subjects
Ridge waveguide lasers ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Slope efficiency ,Wide-bandgap semiconductor ,Optoelectronics ,Spontaneous emission ,High current ,business ,Quantum well ,Leakage (electronics) ,Semiconductor laser theory - Abstract
In this paper, the carrier transport in (Al)InGaN based test structures with In-rich quantum wells on c-plane substrates is investigated under high current operation. To get access to the injection efficiency, the devices are processed as ridge waveguide lasers and examined above threshold. The slope efficiency reveals a slight decrease as a function of current even under pulsed operation that can be related to a reduction of the injection efficiency based on carrier leakage. As the test structure contains an InGaN detection layer on the n-side, it is possible to verify hole overflow across the active region. Moreover, by analysing the current dependence of the radiative recombination in the detection layer, the reduction of slope efficiency can be correlated to increasing hole leakage.
- Published
- 2013
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