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Conference 11686

Gallium Nitride Materials and Devices XVI

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  • Welcome and Introduction
  • Conference Networking Session
  • Topical Discussion Rounds
  • OPTO Plenary Session
  • Vertical-Cavity Surface-Emitting Lasers (VCSELs)
  • In-Plane Laser Diodes
  • UV Laser Diodes
  • UV LEDs
  • Novel Devices and Micro-/Nanostructures
  • Epitaxy and Bulk Growth
  • Fundamental Physics and Characterization I
  • Fundamental Physics and Characterization II
  • GaN Electronics and HEMTs
  • Poster Session
  • Front Matter: Volume 11686
2021-03-07T14:03:58-08:00
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UPCOMING LIVE EVENTS:
Welcome and Introduction
11686-800
Author(s): Hiroshi Fujioka, Institute of Industrial Science, The Univ. of Tokyo (Japan); Hadis Morkoç, Virginia Commonwealth Univ. (United States); Ulrich T. Schwarz, Technische Univ. Chemnitz (Germany)
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Introduction to SPIE Photonics West OPTO conference 11686: Gallium Nitride Materials and Devices XVI.
Conference Networking Session
11686-700
8 March 2021 • 2:00 PM - 3:00 PM PST
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Meet colleagues interested in this conference topic for small group discussion and networking, hosted by the conference chairs. We will briefly introduce how to interact during the conference, with slack as communication tool, and present an outline of the program of this conference. While this informal session emphasizes conversation rather than talk delivery, it is also an entry point into two-way discussions during this virtual conference. Hosted By: Hiroshi Fujioka, Institute of Industrial Science, The Univ. of Tokyo (Japan); Hadis Morkoç, Virginia Commonwealth Univ. (United States); Ulrich T. Schwarz, Technische Univ. Chemnitz (Germany).
Topical Discussion Rounds
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 8-March at 4:00 PM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on epitaxy and bulk growth of group-III-nitrides. Hosted by: Russell D. Dupuis, Georgia Institute of Technology (United States).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 8-March at 9:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on epitaxy and bulk growth of group-III-nitrides. Hosted by: Motoaki Iwaya, Meijo Univ. (Japan) and Michal Bockowski, Institute of High Pressure Physics (Poland).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 9-March at 9:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on fundamental physics and characterization of gallium nitride materials and devices. Hosted by: Kazunobu Kojima, Tohoku Univ. (Japan) and Martin Feneberg, Otto-von-Guericke-Univ. Magdeburg (Germany).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 9-March at 12:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on fundamental physics and characterization of gallium nitride materials and devices. Hosted by: Pei-Cheng Ku, Univ. of Michigan (United States).
11686-705
9 March 2021 • 4:00 PM - 5:00 PM PST
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 10-March at 12:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on UV LEDs and laser diodes. Hosted by: Hideto Miyake, Mie Univ. (Japan).
11686-706
10 March 2021 • 12:00 AM - 1:00 AM PST
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 9-March at 4:00 PM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on UV LEDs and laser diodes. Hosted by: Michael Kneissl, Technische Univ. Berlin (Germany) and Matteo Meneghini, Univ. degli Studi di Padova (Italy).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 10-March at 4:00 PM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on (Al,Ga,In)N laser diodes and vertical-cavity surface-emitting lasers (VCSELs). Hosted by: Åsa Haglund, Chalmers Univ. of Technology (Sweden) and Piotr Perlin, Institute of High Pressure Physics (Poland).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 10-March at 9:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on (Al,Ga,In)N laser diodes and vertical-cavity surface-emitting lasers (VCSELs). Hosted by: Tetsuya Takeuchi, Meijo Univ. (Japan).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 11-March at 9:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on novel devices and micro-/nanostructures and GaN electronics and HEMTs. Hosted by: Ulrich T. Schwarz, Technische Univ. Chemnitz (Germany).
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This will be a live online Discussion Round focused on an individual topic where smaller number of people can meet. There is a second meeting scheduled on this topic at on 11-March at 12:00 AM PST to accommodate different time zones. There is no limit to discussion, however, there is a suggested focus for each Round. This Round will focus on novel devices and micro-/nanostructures and GaN electronics and HEMTs. Hosted by: Lars Samuelson, Lund Univ. (Sweden) and Matthew T. Hardy, U.S. Naval Research Lab. (United States).
OPTO Plenary Session
11691-201
Silicon photonics breaks new ground (Plenary Presentation)
Author(s): Graham T. Reed, Optoelectronics Research Ctr. (United Kingdom)
9 March 2021 • 12:05 PM - 12:35 PM PST
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Silicon photonics has emerged as a game-changing technology for data communications in recent years. However, the technology is also applicable to an increasing number of other applications. Even in the data-comm application, the relentless demand for more data requires the performance of silicon photonics to continue to improve. In this presentation I will discuss our work in three aspects of Silicon Photonics technology. The first is high-speed optical transmitters. Our approach of co-design of the photonic and electronic components of systems has enabled us to demonstrate 100Gb/s OOK from a single silicon modulator without any equalisation. Secondly, I will discuss a technology that we have developed that allows comprehensive wafer scale testing of silicon photonics circuits, as well as trimming of individual devices, and a non-volatile method of programming silicon photonics circuits without the need for large power consumption to maintain the state of the programmed circuit. Finally, I will discuss our work with Pointcloud Inc., on 3D imaging via an integrated LIDAR system, which has demonstrated millimeter accuracy for measurements made at distances beyond 70m.
11689-202
Author(s): Kerry J. Vahala, Caltech (United States)
9 March 2021 • 12:45 PM - 1:15 PM PST
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Electronics and photonics have long had a complementary coexistence across multiple application areas. Nonetheless, an ideal partnership of these two realms was made challenging in large part by the enormous frequencies of lightwaves. About two decades ago, this limitation was overcome with the invention of the laser frequency comb. Combs provide a coherent link between electronics and photonics, and because the link is bidirectional, performance attributes previously unique to each can now be shared. Their implementation has been transformative for time keeping, frequency metrology, precision spectroscopy, microwave-generation, ranging and other technologies. More recently still, high-Q nonlinear optical microresonators, have enabled chip-scale frequency combs. I will review efforts to fully integrate comb systems around these new ‘microcombs,’ along with the physical principles of the devices themselves. Finally, I will consider the revolutionary impact this chip-scale unification of the optoelectronic spectrum can have on photonic instrumentation and consumer products.
11709-203
Author(s): Kohji Mitani, NHK Japan Broadcasting Corp. (Japan)
9 March 2021 • 1:25 PM - 1:55 PM PST
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Japan Broadcasting Corporation (NHK) Science & Technology Research Laboratories (STRL) has long been consistently opening up new horizons for broadcasting. Its recent R&D on 8K ultra-high-definition television―the ultimate two-dimensional television―came to fruition as a regular satellite broadcasting service in Japan in December 2018, with 8K gradually penetrating media and other industries globally. The 8K specifications were determined based on psychophysical experiments to effectively produce an immersive and realistic experience with a two-dimensional screen. STRL is continuing to enhance user experiences. Aside from two-dimensional displays, today there are media devices such as head-mounted displays, augmented reality glasses, three-dimensional displays, and haptic devices. STRL is researching these devices to enhance their performance from the perspective of visual psychology and cognitive science. It is also developing three-dimensional information processing technologies and artificial intelligence aiming for new content presentations with new immersive devices. Conveying sensations other than sight and sound will create innovative sensory experiences that provide unprecedented immersion. A new media scheme that utilizes various delivery platforms such as broadcasting, the internet, and 5G is also being studied to produce new viewing experiences.
Vertical-Cavity Surface-Emitting Lasers (VCSELs)
11686-1
Author(s): Kenichi Terao, Hitoshi Nagai, Daisuke Morita, Shingo Masui, Tomoya Yanamoto, Shin-ichi Nagahama, Nichia Corp. (Japan)
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We will present the latest development results of GaN-based blue and green VCSEL. Our structure which was including AlInN/GaN DBR, n-type, active, and p-type layers was grown on C-plane free-standing GaN substrates by using metal organic chemical vapor deposition (MOCVD). Then, indium tin oxide (ITO) layer for p-contact and SiO2/Nb2O5 dielectric DBR were fabricated. Threshold current of our blue VCSEL reached to less than 1 mA, and maximum optical output power exceeded 1 mW. In addition, lasing over the entire 2-inch wafer was confirmed and high yield was obtained. We will also report the development progress of our green VCSEL.
11686-2
Author(s): Filip Hjort, Chalmers Univ. of Technology (Sweden); Johannes Enslin, Munise Cobet, Technische Univ. Berlin (Germany); Michael A. Bergmann, Joachim Ciers, Chalmers Univ. of Technology (Sweden); Giulia Cardinali, Nando Prokop, Technische Univ. Berlin (Germany); Tim Kolbe, Ferdinand-Braun-Institut (Germany); Felix Nippert, Markus R. Wagner, Technische Univ. Berlin (Germany); Johan S. Gustavsson, Chalmers Univ. of Technology (Sweden); Tim Wernicke, Michael Kneissl, Technische Univ. Berlin (Germany); Åsa Haglund, Chalmers Univ. of Technology (Sweden)
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We will give an overview of the progress in ultraviolet-emitting vertical-cavity surface-emitting lasers (VCSELs) and their potential applications in areas such as disinfection and medical therapy. This includes our demonstration of the shortest wavelength VCSEL, emitting at 310 nm under optical pumping, and a detailed analysis of its filamentary lasing characteristics. The UVB-emitting AlGaN-based VCSEL was realized by substrate removal using electrochemical etching, enabling the use of two high-reflectivity dielectric distributed Bragg reflectors. The potential of using this or alternative methods to push the emission to shorter wavelengths will be examined as well as concepts to realize electrically injected devices.
11686-3
Author(s): Tetsuya Takeuchi, Satoshi Kamiyama, Motoaki Iwaya, Meijo Univ. (Japan); Isamu Akasaki, Meijo Univ. (Japan), Nagoya Univ. (Japan)
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We will show our two recent results related to GaN-based VCSELs with AlInN/GaN DBRs. One is in-situ wafer curvature control of AlInN/GaN DBRs. Curvature data successfully provides us the strain condition in the AlInN layers, which leads to a high reproducibility for fabricating the AlInN/GaN DBRs. The other is laser operation of the VCSELs with large current apertures. While our previous VCSELs with only 8-15 µm apertures showed RT CW operations, our recent VCSELs now show RT CW operations with 5-30 µm apertures. such larger apertures will eventually provide much higher LOPs in the future.
11686-4
Author(s): Tien-Chang Lu, Tsu-Chi Chang, Lih-Ren Chen, Kuo-Bin Hong, Shuo-Yi Kuo, National Chiao Tung Univ. (Taiwan)
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The development of GaN-based vertical-cavity surface-emitting lasers (VCSELs) has been progressing rather fast in the past few years. Owing to the special device structures of GaN-based VCSELs, novel designs have to be incorporated in order to achieve high performance in terms of low threshold, high efficiency, stable mode profile and polarization direction. We demonstrate an easy and cost-effective way to realize index-guiding structure that significantly lowers the threshold and observe the transverse mode spectra of guiding and antiguiding VCSELs. We also realize the GaN-based VCSEL with high-contrast grating (HCG) as the top mirror and achieve polarization control over manipulation of HCG parameters.
11686-5
Author(s): Jin-Ho Kang, Rami T. Elafandy, Jung Han, Yale Univ. (United States)
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Epitaxial, dielectric, and nanoporous DBRs have been actively studied for the demonstration of manufacturable III-nitrides from green to UV. We will discuss these DBR technologies and the advantages of nanoporous DBRs as well as the nano-engineering based on electrochemistry to create nanoporous (Al)GaN.
11686-6
Author(s): Joachim Ciers, Michael A. Bergmann, Filip Hjort, Chalmers Univ. of Technology (Sweden); Jean-François Carlin, Nicolas Grandjean, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Åsa Haglund, Chalmers Univ. of Technology (Sweden)
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III-nitride membranes offer novel device designs in photonics, electronics and optomechanics. However, substrate removal often leads to a rough back surface, which degrades device performance. Here, we demonstrate GaN membranes with atomically smooth etched surfaces by electrochemical lift-off, through the implementation of a built-in polarization field in the sacrificial layer. This leads to a faster reduction in the sacrificial layer free carrier density during etching and thus an abrupter etch stop, reducing the root-mean-square roughness down to 0.4 nm over 5×5 µm2. These results open interesting perspectives on high-quality optical cavities and waveguides in the ultraviolet and visible.
In-Plane Laser Diodes
11686-7
Author(s): Lukas Uhlig, Dominic J. Kunzmann, Yijie Mu, Ulrich T. Schwarz, Technische Univ. Chemnitz (Germany)
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Blue InGaN/GaN broad-ridge laser diodes show rich lateral mode dynamics and filamentation effects in addition to the longitudinal mode dynamics that are known from narrow-ridge laser diodes. We find a complex spectral, spatial and temporal behavior caused by the interplay between lateral and longitudinal mode competition mechanisms. In the experiment we measure the spectral-temporal dynamics with a streak camera, and the lateral resolution is achieved by scanning through a magnified near-field image. Additional time-averaged measurements with a high-resolution spectrometer indicate the presence of multiple longitudinal mode combs and the lateral scans show that there are different lateral modes in each mode comb. But also in separate regions of the laser spectrum, lateral modes of different order can be found.
11686-8
Author(s): Anna Kafar, Piotr Perlin, Szymon Stanczyk, Dario Schiavon, Institute of High Pressure Physics (Poland)
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For certain, growing, class of applications it is necessary to have better suiting combination of beam and spectral quality. This specific combination of beam quality and spectrally broad emission can be delivered by superluminescent diodes (SLEDs). Additionally, the expected advent of nitride integrated photonic circuits and visible light communication call for new active optical elements, such as optical semiconductor amplifiers (SOA). Within this work we will present the progress in the development of broad spectral emission (>15 nm and OSA amplifiers which reach the gain of 10-20 dB at violet-blue wavelength range.
11686-9
Author(s): Takeshi Kamikawa, KYOCERA Corp. (Japan); Srinivas Gandrothula, Hongjian Li, Solid State Lighting & Energy Electronics Ctr. (United States); Valeria Bonito-Olivia, Univ. degli Studi di Trieste (Italy); Feng Wu, Daniel Cohen, James Speck, Steven Denbaars, Shuji Nakamura, Solid State Lighting & Energy Electronics Ctr. (United States)
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A non-polar Fabry-Perot (FP) GaN laser has been demonstrated after the removal of its native free-standing GaN substrate, which was achieved using a new laser fabrication method. Threshold current density of the m-plane laser was measured to be as low as 2.15 kA/cm2 and the operating wavelength is 408.1nm. The method used an epitaxial lateral overgrowth and cleavable technique to remove the laser device from the GaN substrate. Moreover, the reported fabrication method can be applied to realize semi-polar devices from free-standing GaN semi-polar substrates.
11686-10
Author(s): Laurent Lablonde, Catherine Le Rouzic, Thierry Robin, iXblue SAS (France); Antoine Congar, Stéphane Trebaol, Mathilde Gay, Georges Perin, Univ. de Rennes 1 (France); Dominique Mammez, Jean-Claude Simon, Ecole Nationale Supérieure des Sciences Appliquées et de Technologie (France); Pascal Besnard, Univ. de Rennes 1 (France); Julien Rouvillain, Thierry Georges, Oxxius SA (France)
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We report on a fiber Bragg grating external cavity InGaN edge-emitting laser diode showing a stable single longitudinal mode regime with a few mW output power around 400 nm and a side-mode-suppression ratio close to 50 dB. We will study the influence of the cavity length with different fiber types (SM or PM). Assessment will focus on the sub-MHz integrated linewidth and a detailed intensity and frequency noise analysis in the single-frequency regime emission completed by a first-time investigation on the stability of the FBG for guided light at NUV wavelengths.
11686-11
Author(s): Dominic J. Kunzmann, Ulrich T. Schwarz, Technische Univ. Chemnitz (Germany)
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Blue multisection laser diodes are being used before for short pulse applications with high output powers. Hysteresis effects in the current-optical output power (IP) characteristics due to absorption and saturation are known. We additionally observed hysteresis effects in the current-forward voltage (IV) characteristics of these diodes. The voltage increases at the lasing onset current which is different from some observations before. We explain this rise with the shielding of the piezoelectric field, which exists due the stress of the material, due to an increased carrier density below the onset current.
UV Laser Diodes
11686-12
Author(s): Maki Kushimoto, Nagoya Univ. (Japan); Ziyi Zhang, Nagoya Univ. (Japan), Asahi Kasei Corp. (Japan); Naoharu Sugiyama, Yoshio Honda, Nagoya Univ. (Japan); Leo J. Schowalter, Nagoya Univ. (Japan), Crystal IS, Inc. (United States); Chiaki Sasaoka, Hiroshi Amano, Nagoya Univ. (Japan)
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In this presentation, we report on the recently realized pulse current injected UV-C laser diodes (LDs) at room temperature. We have designed and fabricated AlGaN-based LD structures using AlN substrates. The p-type conductivity control was achieved by introducing distributed polarization doping technique into the p-clad design. We have also developed an on-wafer UV-C LD fabrication technology to enable the entire process to be performed on a 2-inch wafer, while suppressing mirror variation, which is a drawback of the conventional cleaving method.
11686-13
Author(s): Motoaki Iwaya, Shunya Tanaka, Moe Shimokawa, Yuya Ogino, Tomoya Omori, Kazuki Yamada, Sayaka Ishizuka, Shohei Teramura, Meijo Univ. (Japan); Kosuke Sato, Meijo Univ. (Japan), Asahi Kasei Corp. (Japan); Sho Iwayama, Meijo Univ. (Japan), Mie Univ. (Japan); Tetsuya Takeuchi, Satoshi Kamiyama, Meijo Univ. (Japan); Isamu Akasaki, Meijo Univ. (Japan), Nagoya Univ. (Japan); Hideto Miyake, Mie Univ. (Japan)
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Ultraviolet (UV) semiconductor lasers are widely used in medical and industrial applications, and their commercialization is strongly desired. Recently, laser oscillation by current injection in the UV-C and UV-B regions has been reported . From now on, it is necessary to demonstrate CW operation, which is indispensable for practical applications. In order to realize this, it is important to understand the internal loss and optical gain of the current devices. In this presentation, we report the details of our UV-B lasers. Specifically, we would like to discuss the results of the variable stripe length analysis of the internal loss of the obtained device and the performance of the UV-B lasers. The results show that the internal losses of the optimized UV-B laser are relatively low and good values are obtained. We also discuss the details of polarization doping, which is very effective in the realization of these UV lasers.
11686-15
Author(s): Sergi Cuesta Arcos, CEA-Grenoble (France); Quang Minh Thai, Univ. Lyon 1 (France); Yoann Curé, CEA-Grenoble (France); Fabrice Donatini, Institut NÉEL (France); Edith Bellet-Amalric, CEA-DRF (France); Catherine Bougerol, Gilles Nogues, Institut NÉEL (France); Olivier Boisron, Sylvain Hermelin, Stephen T. Purcell, Institut Lumière Matière (France); Le Si Dang, Institut NÉEL (France); Eva Monroy, CEA-Grenoble (France)
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There is a strong demand for UV lasers for applications in industry, medical and biochemical domains. These functionalities are currently covered at fixed wavelengths by gas lasers or lasers based on frequency conversion. Here, we present the design and fabrication of electron-beam pumped lasers based on AlGaN/GaN heterostructures to ensure wavelength tunability from UVA to UVC domains. Multi-Quantum-Well SCHs and GRINSCHs were designed for 7-10 kV electron beam pumping using Monte Carlo simulations. Laser cavities were optically characterized and lasing was achieved using a 266 nm Nd:YAG laser, with thresholds as low as 25 kW/cm2.
UV LEDs
11686-16
Author(s): Julien Brault, Mohamed Al Khalfioui, Mathieu Leroux, Ctr. de recherche sur l'hétéroepitaxie et ses applications (France); Samuel Matta, Riber (France); Thi-Huong Ngo, Lab. Charles Coulomb (France); Aly Zaiter, Aimeric Courville, Benjamin Damilano, Sébastien Chenot, Jean-Yves Duboz, Jean Massies, Ctr. de recherche sur l'hétéroepitaxie et ses applications (France); Pierre Valvin, Bernard Gil, Univ. de Montpellier (France)
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AlyGa1-yN quantum dots (QDs), with an Al concentration ranging from 10% to 40%, are grown by molecular beam epitaxy and used as the active region of deep UV light emitting diodes (LEDs). AlxGa1-xN LEDs are seen as the next UV technology for medical and environmental applications. However, their efficiency needs to be improved. Our approach to reach high radiative and injection efficiencies is to combine QDs and tunnel junctions, respectively. We investigate the influence of growth conditions on the QD optical properties and fabricate LEDs emitting in the UVB and UVC regions. The main characteristics of the LEDs are presented.
11686-17
Author(s): Kenjiro Uesugi, Ding Wang, Kanako Shojiki, Shigeyuki Kuboya, Hideto Miyake, Mie Univ. (Japan)
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A combination of the sputtering deposition and high-temperature annealing is a promising technique for preparing low-dislocation-density AlN templates. In this talk, MOVPE growth behavior of AlGaN films grown on the annealed AlN templates and on conventional MOVPE-grown AlN templates was comprehensively discussed. The low density of screw- and mixed-type dislocations of the annealed AlN templates invoked the formation of hillock structures. By adjusting the MOVPE growth conditions and utilizing sapphire substrates with appropriate surface off-cut, dislocation-induced hillock structures were suppressed. Improved surface flatness resulted in higher EQE and better wavelength uniformity of the DUV-LED fabricated on the annealed AlN templates.
11686-18
Author(s): Rémy Vermeersch, CEA (France); Alexandra-Madalina Siladie, CEA-Grenoble (France); Gwénolé Jacopin, Institut NÉEL (France); Ana Cros, Nuria Garro, Univ. de València (Spain); Eric Robin, CEA-DRF (France); Damien Caliste, Pascal Pochet, CEA-LETI (France); Fabrice Donatini, Julien Pernot, Institut NÉEL (France); Bruno Daudin, CEA-LETI-DOPT (France)
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Using Si for n-type doping and Mg/In co-doping for p-type, AlN nanowire p-n junctions were demonstrated [1]. Optimal electrical activation of acceptor impurities was achieved by electron irradiation. Current voltage characteristics in forward bias conditions have established that the current was varying as Vn, (with n larger than 6) before activation while a space charge limited current regime was observed after activation. The formation of AlN NW p-n junction was assessed by electron beam induced current (EBIC) experiments, putting in evidence the electrical field associated with the junction. [1] A. M. Siladie et al, Nano Lett. 2019, 19, 8357−8364
11686-19
Author(s): Mitsuru Funato, Yoichi Kawakami, Kyoto Univ. (Japan)
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GaN/AlN ultrathin quantum wells (QWs) were grown by metalorganic vapor phase epitaxy using a self-limiting process of GaN thickness to the monolayer (ML) level. 1 ML GaN/AlN QWs emit at 225 nm. The photoluminescence (PL) intensity ratio between low and room temperatures is improved from 0.1% for a conventional AlGaN-based QW emitting at 235 nm to 5% the 1 ML GaN QW. Further improvement to 50% was achieved by an ultrathin GaN QW on r-plane, showing promise of ultrathin GaN QWs as efficient UV emitters.
11686-20
Author(s): Hideki Hirayama, RIKEN (Japan); Yukio Kashima, Eriko Matsuura, Marubun Corp. (Japan); Noritoshi Maeda, RIKEN (Japan); Masafumi Jo, RIKEN Ctr. for Brain Science (Japan); Yasushi Iwaisako, Nippon Tungsten Co., Ltd. (Japan); Takeshi Iwai, Tokyo Ohka Kogyo Co., Ltd. (Japan); Mitsunori Kokubo, Takaharu Tashiro, Toshiba Machine Co., Ltd. (Japan); Kanji Furuta, Ryuichiro Kamimura, Tamato Osada, ULVAC, Inc. (Japan); Hideki Takagi, Yuuichi Kurashima, National Institute of Advanced Industrial Science and Technology (Japan); Tsugumu Nagano, Dai Nippon Printing Co., Ltd. (Japan)
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We demonstrated an enhancement of light-extraction efficiency (LEE) in an AlGaN UVC light-emitting diode (LED) using photonic-crystal (PhC)-reflector fabricated on a p-GaN contact layer, which was introduced to realize both of low resistivity and high-reflectivity in p-contact layer. We fabricated an AlGaN UVC-LED with PhC-reflector on p-GaN contact layer, and confirmed that the external quantum efficiency (EQE) was increased by 1.7 times by introducing PhC-reflector. We also fabricated flip-chip UVC LED with PhC-reflector on p-contact layer and obtained more than 50 mW output power.
11686-21
Author(s): Michael Kneissl, Giulia Cardinali, Johannes Enslin, Christian Kuhn, Martin Guttmann, Frank Mehnke, Luca Sulmoni, Norman Susilo, Tim Wernicke, Technische Univ. Berlin (Germany); Hyun Kyong Cho, Johannes Glaab, Jan Ruschel, Sylvia Hagedorn, Neyhsa Lobo-Ploch, Carsten Netzel, Jens Rass, Sven Einfeldt, Markus Weyers, Ferdinand-Braun-Institut (Germany)
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Driven by applications like monitoring of combustion engines, toxic gases, nitrates in water, as well as the inactivation of multi-drug-resistant germs, the development of AlGaN-based light emitting diodes in the deep ultraviolet spectral range (DUV-LEDs) has markedly intensified. This paper will provide a review of recent advances in development of DUV-LEDs, including the realization of low defect density AlGaN heterostructures on sapphire substrates. The performance characteristics of DUV LEDs emitting in the wavelength range between 260 nm and 217 nm will be discussed and milli-Watt power LEDs near 233 nm will be demonstrated.
11686-22
Author(s): Hideto Miyake, Kenjiro Uesugi, Shiyu Xiao, Kanako Shojiki, Shigeyuki Kuboya, Mie University (Japan)
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For the realization of highly efficient deep-ultraviolet light-emitting diodes (DUV-LEDs) based on III-nitride semiconductors, it is essential to improve the crystalline quality of the AlN templates for crystal growth of AlGaN. Our group has suggested sputtering deposition and post-deposition high-temperature face-to-face annealing (FFA) as a fabrication method of AlN films with low threading dislocation density (TDD) on sapphire substrates. Although the FFA enables reduction of TDDs, it possibly causes a cracking for AlN films due to a large thermal expansion coefficient mismatch between AlN and sapphire. In this work, we controlled the residual stress in AlN films by modifying the sputtering conditions. Consequently, we achieved crack-free AlN films with low TDDs.
11686-23
Author(s): Ram Chandra Subedi, Jung-Wook Min, Somak Mitra, Kuang-Hui Li, Idris Ajia, Edgars Stegenburgs, Dalaver H. Anjum, King Abdullah Univ. of Science and Technology (Saudi Arabia); Michele Conroy, Kalani Moore, Ursel Bangert, Univ. of Limerick (Ireland); Iman S. Roqan, Tien Khee Ng, Boon S. Ooi, King Abdullah Univ. of Science and Technology (Saudi Arabia)
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11686-24
Author(s): Francesco Piva, Carlo De Santi, Matteo Buffolo, Univ. degli Studi di Padova (Italy); Manato Deki, Institute of Materials and Systems for Sustainability (Japan); Maki Kushimoto, Institute of Materials and Systems for Sustainability (Japan); Hiroshi Amano, Institute of Materials and Systems for Sustainability (Japan); Hidemasa Tomozawa, Naoki Shibata, Nikkiso Co., Ltd. (Japan); Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini, Univ. degli Studi di Padova (Italy)
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The aim of this paper is the modeling of the degradation mechanisms of an AlGaN-based UV LED with a nominal wavelength of 285 nm. We analyzed the behavior of the device during a constant current stress at the current of 250 mA, through electrical, optical and spectral measurements and SSPC analysis. We found the presence of two different degradation mechanisms, the first one (before 1000 min) ascribed to a decrease in the injection efficiency due to the de-hydrogenation of gallium vacancies, the second one (after 1000 min) ascribed to the generation of midgap defects detected from the SSPC analysis.
11686-25
Author(s): Michael A. Bergmann, Chalmers Univ. of Technology (Sweden); Johannes Enslin, Martin Guttmann, Luca Sulmoni, Technische Univ. Berlin (Germany); Neysha Lobo-Ploch, Ferdinand-Braun-Institut (Germany); Filip Hjort, Chalmers Univ. of Technology (Sweden); Tim Kolbe, Ferdinand-Braun-Institut (Germany); Tim Wernicke, Technische Univ. Berlin (Germany); Michael Kneissl, Technische Univ. Berlin (Germany), Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (Germany); Åsa Haglund, Chalmers Univ. of Technology (Sweden)
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We here demonstrate thin-film flip-chip (TFFC) ultraviolet-B light-emitting diodes (LEDs) fabricated by a standard LED process and followed by a substrate removal based on selective electrochemical etching of an n-doped multilayered Al0.11Ga0.89N/Al0.37Ga0.63N sacrificial layer. The integration of the LEDs to a Si carrier using thermocompression bonding allowed roughening of the N-polar AlGaN side of the TFFC LEDs using TMAH-etching, which increased the light extraction efficiency by approximately 45% without negatively affecting the I-V-characteristics. This resulted in an optical output power of 0.47 mW at 10 mA for an LED with a p-contact area of 0.03 mm2.
Novel Devices and Micro-/Nanostructures
11686-27
Author(s): Marzieh Bakhtiary-Noodeh, Minkyu Cho, Zhiyu Xu, Hoon Jeong, Nepomuk Otte, Shyh-Chiang Shen, Theeradetch Detchprohm, Georgia Institute of Technology (United States); Ashok K. Sood, John W. Zeller, Magnolia Optical Technologies, Inc. (United States); Parminder Ghuman, Sachidananda Babu, NASA Earth Science Technology Office (United States); Russell D. Dupuis, Georgia Institute of Technology (United States)
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GaN avalanche photodiodes can exhibit high detection sensitivity and low dark current making them candidates for many applications. Mesa etching is one of the major challenges in fabrication of these devices, which is one of the sources of leakage currents and premature breakdown. In this work, GaN APDs were grown by MOCVD on GaN substrates and processed using ion-implantation isolation to reduce the sidewall leakage current and improve reliability. An avalanche gain ~7x105 was obtained. Ion-implanted devices show a dark current density <10-9A/cm2 at VR=-40V, while the conventional mesa-etched APDs show three orders of magnitude higher dark current density
11686-28
Author(s): Yasufumi Fujiwara, Shuhei Ichikawa, Dolf Timmerman, Jun Tatebayashi, Osaka Univ. (Japan)
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Development of an efficient red LED based on GaN is pivotal to ultra-small-size, full-color, and high-resolution micro-LED displays. In a red LED using Eu-doped GaN (GaN:Eu), the peak position of the emission is extremely stable against ambient temperature and injected current. Photoluminescence quantum efficiency of the Eu emission was investigated as a function of chip size of square structures. Even for sizes smaller than 24 µm, an influence of sidewall-related non-radiative recombination of carriers on the quantum efficiency was only minor as a result of limited carrier diffusion lengths in GaN:Eu. We also demonstrated monolithic vertically stacked full-color LEDs consisting of GaN:Eu and InGaN quantum wells. These results indicate a high potential of the GaN:Eu LED for the micro-LED applications.
11686-29
Author(s): Lars Samuelson, Lund Univ. (Sweden)
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III-Nitride based light-emitting diodes based on InGaN active layers formed on GaN, are fine for the blue and green emitting LEDs. However, the large lattice mis-match between red-emitting active layers and the GaN substrate still limits the efficiencies to very low values, typically <5%. We propose to use seeding techniques originally developed for nanowire growth, to seed the formation of ternary InGaN pyramids which later are converted to thin c-facet platelets of InGaN. I will in this presentation show that such relaxed, and dislocation-free, InGaN platelets with In-composition about 20%, have the potential as ideal templates for red-emitting microLEDs.
11686-31
Author(s): Daisuke Iida, Zhe Zhuang, Pavel Kirilenko, Martin Velazquez-Rizo, Mohammed A. Najmi, Kazuhiro Ohkawa, King Abdullah Univ. of Science and Technology (Saudi Arabia)
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We obtained the EL intensity enhancement by a factor of 1.3 with increasing of n-GaN thickness from 2 to 8 µm. We achieved a light output, forward voltage, FWHM and external quantum efficiency of 0.64 mW, 3.3 V, 59 nm, and 1.6% at 20 mA, respectively. Particularly, the wall plug efficiency was 1.0%, which is comparable with the state-of-the-art InGaN-based red LEDs. The reduction of the in-plane compressive stress by the GaN underlying layers appears to be crucial for enhancing the light output of InGaN-based red LEDs on conventional sapphire substrates.
11686-32
Author(s): Soufiane Karrakchou, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France); Suresh Sundaram, Georgia Tech-Lorraine (France), Georgia Tech - CNRS (France); Taha Ayari, Adama Mballo, Phuong Vuong, Georgia Tech - CNRS (France); Ashutosh Srivastava, Rajat Gujrati, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France); Ali Ahaitouf, Georgia Tech-Lorraine (France), Georgia Tech - CNRS (France), Univ. Sidi Mohammed Ben Abdellah de Fès (Morocco); Paul L. Voss, Jean-Paul Salvestrini, Abdallah Ougazzaden, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France)
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We present a critical study of LEDs on h-BN compared to the conventional LEDs on sapphire from materials characterizations, device fabrication to the device performances measurements performed before and after liftoff and transfer with and without intermediary adhesion layer to arbitrary substrates
11686-33
Author(s): Renji Okuda, Weifang Lu, Meijo Univ. (Japan); Naoki Sone, Meijo Univ. (Japan), Koito Manufacturing Co., Ltd. (Japan); Yoshiya Miyamoto, Kazuma Ito, Kazuyoshi Iida, Meijo Univ. (Japan); Koji Okuno, Koichi Mizutani, Meijo Univ. (Japan), Toyoda Gosei Co., Ltd. (Japan); Satoshi Kamiyama, Tetsuya Takeuchi, Motoaki Iwaya, Isamu Akasaki, Meijo Univ. (Japan)
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We report on the development of laser devices (LDs) fabrication on coaxial multiple-quantum-shell (MQS) nanowires. The MQS nanowires were grown with thin p-GaN shell, tunnel junction and a n-GaN cap layer by metalorganic chemical vapor deposition. Index guided stipe structures were fabricated on the sample, wherein optimized dry and wet etching processes were applied to form mirror on the sidewall. Afterwards, the electronic properties of the MQS laser devices were characterized by current-voltage measurement. Under a high direct-current (DC) density of 3 kA/cm2, uniform blue-light emission was confirmed over the entire stripe.
11686-34
Author(s): Emma Rocco, Kasey Hogan, Vincent Meyers, Ben McEwen, SUNY Polytechnic Institute (United States); Lloyd Douglas Bell, Jet Propulsion Lab. (United States); F. Shadi Shahedipour-Sandvik, SUNY Polytechnic Institute (United States)
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We report here our latest results of achieving high quantum efficiency (QE) N-polar GaN photocathodes through engineering of bulk and interfacial impurity concentrations. The photocathode structures studied consist of an N-polar p-GaN absorbing layer with 10 nm u-GaN cap layer. An increase in QE from 0.27% to 10.1% is observed for photocathodes grown without a regrowth interface between p-GaN and u-GaN cap layers compared to an identical structure with a regrown interface. SIMS is used to identify impurities at the regrowth interface, which cause lower QE due to scattering and modification of the electric field. The QE is further increased to 26.6% through a 2x increase in hole concentration when the structure is grown on a high hillock density template. This work demonstrates a combined approach that has the promise of advancing toward and surpassing performance of current state-of-the-art photocathodes in the UV range.
11686-36
Author(s): Keshab R. Sapkota, A. Alec Talin, Francois Leonard, Sandia National Labs. (United States); Barbara A. Kazanowska, Univ. of Florida (United States); Brendan P. Gunning, Sandia National Labs. (United States); Kevin S. Jones, Univ. of Florida (United States); George T. Wang, Sandia National Labs. (United States)
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Solid-state, vacuum nanoelectronic devices have the potential to combine the advantages of vacuum electron devices, such as robustness in harsh environments and high frequency operation, and solid-state devices, such as size, integrability, and low-power operation. In this work, we demonstrate novel GaN nanogap field emission diodes that operate in air and exhibit ultra-low turn-on voltage, high field emission current, and excellent on-off ratio. We present experimental and modeling results on the field emission characteristics of these devices at various nanogap sizes and operating pressures. These results provide critical new insights into the behavior of this new class of devices and point to future challenges and opportunities. Sandia National Laboratories is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
Epitaxy and Bulk Growth
11686-37
Author(s): Yoshihiro Kangawa, Kyushu Univ. (Japan), Nagoya Univ. (Japan)
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III-Nitride semiconductors are attractive materials for optoelectronic devices including LEDs and LDs. To enhance the device performances, it is important to prevent impurity incorporation during thin film growth. The knowledge of atomistic-scale phenomena is indispensable to prevent contamination of thin films. In the present work, we model elementary growth processes in GaN MOVPE such as (1) vapor phase reaction, (2) surface reaction and (3) solid-phase diffusion during epitaxy. In this presentation, we discuss incorporation mechanisms of carbon in GaN(0001) and (000-1) MOVPE, and of oxygen in vicinal GaN(10-10) MOVPE.
11686-38
Author(s): Nao Takekawa, Ken Goto, Tokyo Univ. of Agriculture and Technology (Japan); Toru Nagashima, Reo Yamamoto, Tokuyama Corp. (Japan); Junji Kotani, Fujitsu Labs. Ltd. (Japan); Yoshinao Kumagai, Tokyo Univ. of Agriculture and Technology (Japan)
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High-temperature AlN homoepitaxial growth up to 1600℃ by HVPE was investigated. High-purity AlN with excellent crystallinity was reported where HVPE-AlN was homoepitaxially grown on the PVT-AlN substrate. However, quartz-derived impurities incorporation was slightly problematic in the HVPE-AlN. In this study, a new reactor was introduced that is a quartz glass reactor including a high-temperature growth zone constructed with heat-resistant materials. O and Si impurity incorporation was reduced with high growth rates of around 150 μm/h by the newly introduced high-temperature growth system. This work was partially supported by Innovative Science and Technology Initiative for Security Grant Number JPJ004596, ATLA, Japan.
11686-39
Author(s): Abdallah Ougazzaden, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France); Suresh Sundaram, Georgia Tech - CNRS (France), Georgia Tech-Lorraine (France); Phuong Vuong, Adama Mballo, Georgia Tech - CNRS (France); Gilles Patriarche, Ctr. de Nanosciences et de Nanotechnologies (France), Univ. Paris-Saclay (France); Ashutosh Srivastava, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France); Ali Ahaitouf, Georgia Tech - CNRS (France), Georgia Tech-Lorraine (France); Simon Gautier, Tarik Moudakir, Georgia Tech - CNRS (France); Paul L. Voss, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France); Jean Paul Salvestrini, Georgia Institute of Technology (United States), Georgia Tech - CNRS (France), Georgia Tech-Lorraine (France)
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Combined photonic and electronic systems require diverse devices to be co-integrated on a common platform. This heterogeneous integration is made possible through several separation and transfer methods where the functioning epilayers are essentially released from their growth substrate. The use of 2D layered h-BN as a mechanical release layer has been demonstrated to be a promising technique for the hybrid integration of III-nitride devices. In this talk we will give an overview of our results on wafer-scale van der Waals epitaxy by MOVPE of different III-N heterostructure devices such as LEDs, HEMTs, solar cells, sensors and photodetectors. Furthermore, mechanical release and transfer techniques of crack-free III-N devices on foreign substrates will be presented along with a comparison between the device performances before and after transfer.
11686-43
Author(s): Karolina Grabianska, Michal Bockowski, Boleslaw Lucznik, Institute of High Pressure Physics (Poland); Robert Kucharski, Institute of High Pressure Physics (Poland); Tomasz Sochacki, Institute of High Pressure Physics (Poland)
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In this paper we would like to report the recent progress in basic ammonothermal GaN crystal growth. Growth on ammonothermal GaN seeds is presented. Structural properties of the seeds are shown and discussed. A new shape of seed crystals is proposed. It allows to eliminate the appearance of cracks in the growing GaN. The unwanted lateral growth is restricted and controlled. A higher growth rate, both in lateral and vertical directions, is obtained. Generally, the high structural quality of native seeds is maintained. In case of crystallization in lateral directions the structural quality of the seeds can even be improved. The influence of the crystallization run parameters, growth direction and configuration on the structural quality of the obtained GaN will be discussed.
11686-44
Author(s): Kazuma Ito, Weifang Lu, Meijo Univ. (Japan); Naoki Sone, Meijo Univ. (Japan), Koito Manufacturing Co., Ltd. (Japan); Yoshiya Miyamoto, Renji Okuda, Satoshi Kamiyama, Tetsuya Takeuchi, Motoaki Iwaya, Meijo Univ. (Japan); Isamu Akasaki, Meijo Univ. (Japan), Nagoya Univ. (Japan)
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The selective-monolithic growth of coaxial GaInN/GaN NWs was investigated by changing the TEG flow rate, barrier and well growth temperature during MQS growth. In incorporation increased with a higher TEG flow rate. However, In-rich flakes were formed the NWs resulting in the deterioration of crystal quality. Using a higher growth temperature of quantum barriers, abnormal growth at the top of NWs was eliminated. As a result, the CL emission intensity was enhanced. Furthermore, the occurrence of In desorption was suppressed by decreasing the growth temperature of quantum wells. Therefore, these results are promising for NW-based white LEDs.
11686-45
Author(s): Miriam Oliva, Abbes Tahraoui, Thomas Auzelle, Jonas Lähnemann, Lutz Geelhaar, Oliver Brandt, Paul-Drude-Institut für Festkörperelektronik (Germany)
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GaN nanowire (NW) arrays are investigated with the main focus on their uniformity, which is a key requirement for the performance of photonic crystals. The NWs are fabricated by two established top-down approaches which are directly compared and critically discussed in terms of their individual merits and drawbacks. A statistical analysis of NW arrays with a nominal NW spacing of 200 nm and NW diameters of 30–70 nm yields distributions of the spacing (diameter) peaking around their nominal values within standard deviations of 2–6 (3–4) nm, a circularity of 0.88–0.89 and a yield of 99.9%.
11686-46
Author(s): Ryan White, Michel Khoury, Matthew Wong, Stacia Keller, Univ. of California, Santa Barbara (United States); David Sotta, Soitec S.A. (France); Shuji Nakamura, Steven P. DenBaars, Univ. of California, Santa Barbara (United States)
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We examine the MOCVD growth conditions on semi-relaxed InGaN substrates necessary for morphological improvement during epitaxy prior to the active region growth. V-pit defects can propagate through the crystal, causing serious morphological degradation. These defects may also be a source of leakage current if they form a low-resistance path through p-n junction. By employing an InGaN/GaN periodic structure, thick base layers can be grown with the improved morphology. High temperature (HT) GaN interlayers in the InGaN/GaN base layer structure then reduce defects significantly, notably eliminating the V-pit type defect. Resulting microLEDs on these improved base layers exhibit a nearly three order of magnitude reduction in leakage current density at 1V, far below the uLED turn-on threshold, and significantly lower dynamic resistance. This result indicates the improvement in base layer morphology lead to significant electrical performance improvements, enabling LED production.
11686-47
Author(s): Justin C. Goodrich, Damir Borovac, Lehigh Univ. (United States); Chee-Keong Tan, Clarkson Univ. (United States); Nelson Tansu, Lehigh Univ. (United States)
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Efficient p-type doping of III-nitride materials is notoriously difficult due to their large band gaps, intrinsic n-type doping, and the large ionization energy of acceptors. Dilute-anion III-nitride materials are a promising solution for addressing this issue and increasing the activation efficiency of p-type dopants. Upward movement of the valence bands reduces the ionization energy of the dopants, allowing for enhanced p-type conductivity in comparison to the conventional nitrides. Incorporation of a dilute-arsenic impurity into AlN significantly reduces the ionization energy of Mg-acceptors from 500 meV to 286 meV, allowing for a two-order magnitude increase in activation efficiency in 6.25%-As AlNAs.
Fundamental Physics and Characterization I
11686-48
Author(s): Akira Uedono, Univ. of Tsukuba (Japan); Hideki Sakurai, Nagoya Univ. (Japan); Tetsuo Narita, Toyota Central R&D Labs., Inc. (Japan); Kacper Sierakowski, Michal Bockowski, Institute of High Pressure Physics (Poland); Jun Suda, Nagoya Univ. (Japan); Shoji Ishibashi, National Institute of Advanced Industrial Science and Technology (Japan); Shigefusa F. Chichibu, Tohoku Univ. (Japan); Tetsu Kachi, Nagoya Univ. (Japan)
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Vacancies in Mg-implanted GaN were probed using positron annihilation technique. Mg was implanted into GaN with [Mg] = 1E19 /cm3. For an as-implanted sample, the major defect species was identified as Ga-vacancy related defects. The sample was annealed under a nitrogen pressure of 1 GPa in a temperature range of 1000–1480C without a protective capping layer. Comparing with the sample annealed with the capping layer, although no large difference in the defect spices was observed, their concentration was decreased by the cap-less annealing. The diffusion of Mg during annealing was influenced by the presence of residual vacancies. H was unintentionally incorporated into the sample during annealing, and its diffusion property were also affected by vacancies and Mg. A part of this work was supported by MEXT “Research and development of next-generation semiconductor to realize energy-saving society (JPJ005357)” and the Polish National Science Centre through project No 2018/29/B/ST5/00338.
11686-49
Author(s): Patrik Scajev, Saulius Miasojedovas, Vilnius Univ. (Lithuania); Bernard Gil, Lab. Charles Coulomb (France); Hideto Miyake, Mie Univ. (Japan)
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Time-resolved photoluminescence and light-induced transient grating techniques were applied for the comparative investigation of the evolution of the internal quantum efficiency and of the carrier diffusion in AlxGa1-xN (x > 0.6) heterostructures in 80 – 550 K temperature range and for excitations from 1 µJcm-2 to 1 mJcm-2. The decrease of the photoluminescence efficiency measured at high excitations and temperatures is quantitatively correlated to the increase of the diffusion coefficients of carriers and to the increase of their non-radiative recombination rate on vacancies. Complex numerical modelling provides a full set of carrier and exciton recombination parameters.
11686-50
Author(s): Kazunobu Kojima, Tohoku Univ. (Japan)
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The current progress of the omnidirectional photoluminescence (ODPL) spectroscopy for quantifying the internal quantum efficiency (IQE) of a near-band-edge emission in GaN will be reviewed. IQE reflects the concentration of nonradiative recombination centers and deep impurities such as carbon. A prototype of the ODPL spectroscopy was proposed with “2pi-configuration”. However, the 2pi-configuration has a limitation on the sample size due to the integrating sphere used. Therefore, "phi-configuration" was introduced, where the crystal was placed outside the sphere. This allows to cool the sample down to 12 K in vacuum, and to perform a mapping experiment of IQE across the GaN wafers.
11686-51
Author(s): Ryota Ishii, Mitsuru Funato, Yoichi Kawakami, Kyoto Univ. (Japan)
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Photoluminescence spectroscopy using a scanning near-field optical microscope (SNOM) is a powerful technique to study luminescence properties of III-Nitride semiconductors. To date, we have developed a SNOM with an excitation and a detection wavelength of 210 nm and >220 nm, respectively.[1] The deep-ultraviolet (DUV) SNOM has the shortest operation wavelength ever reported and visualizes the localized emission nature of Al-rich AlGaN quantum wells with a spatial resolution exceeding 150 nm. In the presentation, recent progresses of our study using the DUV-SNOM are given. [1] Ishii et al., APL Photonics 4, 070801 (2019).
11686-52
Author(s): Timothée Lassiaz, Pierre Tchoulfian, Aledia (France); Fabrice Donatini, Institut NÉEL (France); Julien Brochet, Romain Parize, Aledia (France); Gwénolé Jacopin, Julien Pernot, Institut NÉEL (France)
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InGaN/GaN core-shell wire-based LEDs are a promising alternative to the c-plane two-dimensional LEDs for µLED display technologies. Developing correlative doping characterization techniques adapted to wires is essential to optimize the epitaxial structure. The impact of different LED growth conditions was investigated through current-voltage (I-V) and capacitance–voltage (C–V) characteristics on both single wire and assembly of wires. A statistical C-V study was carried out on ~70 single wires to evaluate the agreement in depletion width and effective doping level Neff values between single and assembly of connected wires. To corroborate the results, EBIC measurement were also performed to determine the position of the p-n junction and depletion region width.
11686-53
Author(s): Michal Bockowski, Institute of High Pressure Physics (Poland); Kacper Sierakowski, Institute of High Pressure Physics (Poland); Rafal Jakiela, Institute of Physics, Polish Academy of Sciences (Poland); Marcin Turek, Maria Curie-Sklodowska Univ. (Poland); Piotr Jaroszyński, Paweł Kempisty, Michał Fijałkowski, Institute of High Pressure Physics (Poland)
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Diffusion of Be was investigated for the main crystallographic directions in HVPE-GaN: c [0001], m [10-10], and a [11-20]. Be was implanted into the samples at room temperature with a dose of 2.9e15 cm-2 with energy of 200 keV. Ultra-high pressure annealing (UHPA) was performed to repair the post-implantation damage and activate the dopant. The annealing was performed at different time (15 and 30 minutes) and temperature (1200 – 1400°C). Depth profiles of Be were measured by secondary ion mass spectrometry (SIMS). Diffusion coefficients were calculated using the complementary error function (erfc) or Boltzmann-Matano analysis. The determined diffusion coefficients were summarized in an Arrhenius plot: D(1/T). From this relation the pre-exponential factor D0 and the activation energy were calculated. In addition, it was possible to calculate the formation energy for interstitial Be as well as gallium vacancy defects.
11686-54
Author(s): Nathan A. Dvorak, Univ. of Michigan (United States); Kunook Chung, Ulsan National Institute of Science and Technology (Korea, Republic of); Kobie Mueller, Pei-Cheng Ku, Univ. of Michigan (United States)
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A novel force sensor capable of determining both the direction and magnitude of the force is proposed and demonstrated. The sensor structure is based on two orthogonally oriented arrays of GaN (Gallium Nitride) elliptical nanopillars and a digital CMOS (Complementary Metal Oxide Semiconductor) image sensor. Only a common bias, either optical or electrical, is needed across the entire device, making two-dimensional mapping simple and easily completed using a common digital CMOS camera. With a combination of two arrays, we showed that the direction and magnitude of the force can be determined by comparing the emission intensity change between two orthogonal arrays.
11686-55
Author(s): Wei Liu, Ecole Polytechnique Fédérale de Lausanne (Switzerland), UCLA Samueli School of Engineering (United States); Camille Haller, Yao Chen, Thomas Weatherley, Jean-François Carlin, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Gwénolé Jacopin, Institut NÉEL (France); Raphaël Butté, Nicolas Grandjean, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
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We study the impact of non-radiative defects on Auger recombination in c-plane InGaN/GaN single quantum wells (SQWs) in the efficiency droop regime using high injection time-resolved photoluminescence. The defect density in the active layer is tuned by varying the thickness of an InAlN underlayer. When the defect density is increased, apart from Shockley–Read–Hall (SRH) and standard Auger recombination, introducing an extra defect-assisted Auger process is required to reconcile the discrepancy observed between the usual ABC model and experimental data. We derive a linear dependence between the SRH coefficient and the bimolecular defect-assisted Auger coefficient, which suggests that the generated defects can act as scattering centers responsible for indirect Auger processes. Our results further suggest that the defect-assisted Auger recombination is expected to be all the more critical in green to red III-nitride light-emitting diodes due to their reduced radiative rate.
11686-56
Author(s): Francesco Piva, Carlo De Santi, Alessandro Caria, Matteo Buffolo, Univ. degli Studi di Padova (Italy); Camille Haller, Jean-François Carlin, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Mauro Mosca, Univ. degli Studi di Palermo (Italy); Gaudenzio Meneghesso, Enrico Zanoni, Univ. degli Studi di Padova (Italy); Nicolas Grandjean, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Matteo Meneghini, Univ. degli Studi di Padova (Italy)
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In this paper we demonstrated a significant improvement of the performance of InGaN/GaN QW LEDs through the insertion of an InAlN UL. We demonstrated an improvement in both electrical and optical characteristic for the sample with the UL, and a higher concentration of defects in the active region for the sample without the UL. Moreover, we found the presence of two defects, one placed at EC≈2.5 eV, and one placed at the midgap (EC≈1.8 eV), which act as a non-radiative recombination center. At the end, we proposed a model to find the traps distribution in the active region.
Fundamental Physics and Characterization II
11686-57
Author(s): Yoshihiro Ishitani, Kensuke Oki, Masaya Chizaki, Shungo Okamoto, Tomoya Nakayama, Bojin Lin, Bei Ma, Ken Morita, Chiba Univ. (Japan); Hideto Miyake, Mie University (Japan); Daisuke Iida, Kazuhiro Ohkawa, KAUST (Saudi Arabia)
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We have numerically simulated exciton – LO phonon interaction in III-nitride materials. In the temperature range higher than 150 K, the exciton dynamics is dominated by the interaction with the LO phonon. The competition between the interactions with LO phonons and electrons impacts the population distribution among various states, which affects the radiative recombination lifetime and the radiation efficiency when nonradiative recombination process exists. According to the importance of the LO phonon analysis, we have conducted microscopic Raman measurement using simultaneous irradiation of two laser beams, and have successfully detected peculiar properties of LO phonons in nitride thin films.
11686-59
Author(s): Guillaume Cassabois, Univ. de Montpellier (France)
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The growth of high-quality crystals of hexagonal boron nitride (hBN) in 2004 has revealed that hBN is a promising material for light-emitting devices in the deep ultraviolet domain, as illustrated by the demonstration of lasing at 215 nm by accelerated electron excitation, and also the operation of field emitter display-type devices in the deep ultraviolet. Although it was recently understood that hBN is an indirect bandgap semiconductor, the understanding of the optical response close to the bandgap is still an open debate. In hBN, the direct and indirect excitons are close in energy and the dielectric permittivity around 200 nm is expected to be governed by the interplay between direct and indirect transitions. Here I will present our recent reflectivity experiments in high-quality hBN crystals from single monolayer to bulk hBN. I will explain the originality of the dielectric permittivity close to the bandgap of hBN in comparison with other nitride semiconductors.
11686-60
Author(s): Thomas Pelini, Christine Elias, Univ. de Montpellier (France); Ryan Page, Cornell Univ. (United States); James H. Edgar, Kansas State Univ. (United States); Pierre Valvin, Bernard Gil, Guillaume Cassabois, Univ. de Montpellier (France)
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We study shallow and deep levels in carbon-doped hexagonal boron nitride crystals precipitated from a molten metal solution in a high-temperature furnace. Reflectance and photoluminescence under deep ultraviolet excitation are complemented by spatially resolved experiments by means of a scanning confocal micro-photoluminescence setup operating in the ultraviolet. Isotopically controlled carbon doping does not induce any energy shift of the well-known deep-level emission at 4.1 eV. Our detailed characterization in a series of carbon-doped crystals reveals that the incorporation of carbon during the growth process results in a distinct class of shallow and deep levels in hexagonal boron nitride, calling into question the exact role of carbon in the growth of hexagonal boron nitride and its direct or indirect influence on the formation of the crystal defects.
11686-61
Author(s): Eric N. Jin, Matthew T. Hardy, Alyssa L. Mock, John L. Lyons, Alan R. Kramer, Marko J. Tadjer, Neeraj Nepal, D. Scott Katzer, David J. Meyer, U.S. Naval Research Lab. (United States)
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We determine the band alignment of ScxAl1-xN/GaN heterojunctions at ScN alloy fractions ranging from x = 0.04 to 0.20 using x-ray photoemission spectroscopy, and determine the band gap from spectroscopic ellipsometry. We find a transition from straddling to staggered gap as ScN alloy fraction increases, and show that the experimental results are consistent with first-principles calculations. This crossover from type-I to type-II band alignment shows a degree of freedom for engineering improved heterostructures in ScAlN/GaN-based electronic and optoelectronic devices.
11686-62
Author(s): Hanlin Fu, Justin C. Goodrich, Nelson Tansu, Lehigh Univ. (United States)
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The band structure and band alignment for ScxAl1-xN /AlN heterojunctions, with Sc-content x up to 25%, are investigated via first principle density functional theory (DFT) calculations. The supercell approach is utilized to build the crystal structure of ScAlN and AlN alloys and we investigate the natural band offsets of ScxAl1-xN relative to AlN through the potential line-up method. Our calculations suggest a type-I ScAlN / GaN heterostructure with large band offsets. The implementation of ScAlN will have impacts for deep ultraviolet, power electronics, and laser devices.
11686-64
Author(s): Barbara A. Kazanowska, Univ. of Florida (United States); Keshab R. Sapkota, Brendan P. Gunning, Sandia National Labs. (United States); Kevin S. Jones, Univ. of Florida (United States); George T. Wang, Sandia National Labs. (United States)
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AlGaN is a leading candidate for current and future ultra-wide bandgap electronic and optoelectronic applications. However, 3D etch technologies for AlGaInN remain immature compared to silicon, limiting its full potential for novel devices. Here, we build from the foundation of anisotropic KOH-based wet etchants used to fabricate GaN structures and explore AlGaN alloys etched in acids and bases. We investigate the etch reactivity of AlGaN alloys as a function of Al content in various etchants. We then explore the etch evolution of novel nanostructures observed and discuss possible mechanistic explanations. Lastly, we look at field emission properties of AlGaN alloys.
GaN Electronics and HEMTs
11686-67
Author(s): Tamotsu Hashizume, Hokkaido Univ. (Japan); Erika Maeda, National Institute for Materials Science (Japan); Ryota Ochi, Hokkaido Univ. (Japan); Toshihide Nabatame, National Institute for Materials Science (Japan); Koji Shiozaki, Nagoya Univ. (Japan); Taketomo Sato, Hokkaido Univ. (Japan)
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We have investigated AlGaN/GaN high-electron mobility transistors (HEMTs) with a high κ gate dielectric using hafnium silicate (HfSiOx). The (HfO2)/(SiO2) laminate structure was deposited on the AlGaN surface by a plasma-enhanced atomic layer deposition, followed by a post-deposition annealing at 800 ºC. The HfSiOx-gate HEMT showed good transfer characteristics with a high transconductance expected from its κ value and a subthreshold swing of 71 mV/decade. In addition, we observed excellent capacitance-voltage (C-V) characteristics with negligible frequency dispersion in the metal-oxide-semiconductor (MOS) HEMT diode. The detailed C-V analysis showed low state densities in the order of 1011 cm-2 eV-1 at the HfSiOx/AlGaN interface.
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We have performed the operando analysis using synchrotron radiation nanobeam X-ray diffraction (nanoXRD) techniques combined with the pump-probe method to quantitatively analyze strain induced by the inverse piezoelectric effect (IPE) in AlGaN/GaN HEMTs in operation. The c-plane lattice spacing change of the AlGaN barrier depending on applied gate voltage to the device and its transient states were successfully detected with a nanosecond resolution. Since our nanoXRD analysis directly characterizes IPE-induced crystalline lattice structures, it paves the way for novel approaches to elucidate defect formation mechanisms in nitride semiconductor based HEMT devices.
11686-69
Author(s): Yongkun Sin, Dmitry Veksler, William Hubbard, Scott D. Sitzman, Miles Brodie, Zachary Lingley, Neil Ives, The Aerospace Corp. (United States)
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AlGaN-GaN high-electron-mobility-transistors (HEMTs) on SiC substrates are produced for both commercial and defense applications. Although GaN HEMT manufacturers have reported encouraging reliability, long-term reliability remains a major concern especially for space applications due to unknown degradation mechanisms. We investigated RF AlGaN-GaN HEMTs on SiC with Ni-Pd-Au Schottky contacts by performing physics of failure investigation to understand degradation mechanisms. Our findings include defects containing pits, cracks, and pockets of Pd exclusively located at the edge of the drain side of the gate. We provide a model including the out-diffusion of Pd as part of degradation mechanisms in our GaN HEMTs.
Poster Session
11686-71
Author(s): Yi-Chia Tsai, Can Bayram, Univ. of Illinois (United States)
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The band structures of wurtzite and zincblende III-nitrides are aligned by the electron affinities and the band gaps calculated using a unified hybrid density-functional theory. Based on the Anderson’s electron-affinity rule, the conduction (and valence) band offsets of 1.60 (1.15), 2.47 (0.30), and 4.07 (1.45) eV have been extracted for wurtzite GaN/InN, AlN/GaN, and AlN/InN interfaces, where the conduction (and valence) band offsets of 1.85 (0.89), 1.32 (0.43), and 3.17 (1.32) eV have been procured for zincblende GaN/InN, AlN/GaN, and AlN/InN interfaces, respectively. The valence band edges of both wurtzite and zincblende ternary III-nitrides could be linearly interpolated because the dominant anion compositions at the valence band maximum have a weak dependence on the cation mole fractions. Contrarily, the large bowings on the conduction band edges are attributed to the cation-like nature.
11686-72
Author(s): Anjali Harikumar, CEA-DRF (France); Catherine Bougerol, Fabrice Donatini, Institut NÉEL (France); Edith Bellet-Amalric, CEA-DRF (France); Ioanna Dimkou, CEA (France); Quang Min-Thai, Christophe Dujardin, Stephen T. Purcell, Institut Lumière Matière (France); Eva Monroy, CEA-DRF (France)
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There is a soaring demand for UV lamps emitting at 220-270 nm for applications in disinfection. These needs are currently met by mercury lamps, hazardous for heath and the environment. Despite intense studies on UV LEDs, their efficiency remains limited by problems related to electrical injection. Here, we propose electron pumped UV lamps as an alternative to LEDs in this spectral range. For this purpose, superlattices of close-packed self-assembled AlGaN quantum dots are particularly promising, due to their high internal quantum efficiency (around 50%) and promising external quantum efficiency (4% in as-grown material, increasing to 7% by dice polishing).
11686-73
Author(s): Piotr Jaroszynski, Institute of High Pressure Physics (Poland); Karolina Grabianska, Michal Fijalkowski, Mikolaj Amilusik, Institute of High Pressure Physics (Poland); Marcin Zajac, Institute of High Pressure Physics (Poland); Marcin Turek, Maria Curie-Sklodowska Univ. (Poland); Michal Bockowski, Institute of High Pressure Physics (Poland)
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Implantation of Ga ions into ammonothermal GaN crystals is proposed as a method of controlling the concentration of gallium vacancies. Ultra-high pressure annealing (UHPA) is expected to facilitate the diffusion of the implanted Ga ions into the entire volume of the crystal. Gallium vacancies are expected to be replaced by the Ga ions. Since Ga vacancies act as acceptors in GaN, reducing their content will result in a higher free electron concentration in the crystal. Gallium ion implantation and UHPA processes will be presented in detail. Values of the main parameters of UHPA allowing for the complete replacement of the Ga vacancies with Ga ions in GaN crystals will be determined. The morphology as well as structural, optical, and electrical properties will be compared for samples without any treatment and those implanted and annealed. The ultimate goal is to obtain highly conductive GaN crystals with the lowest possible Ga vacancy concentration.
11686-74
Author(s): Daisuke Iida, Zhe Zhuang, Pavel Kirilenko, Martin Velazquez-Rizo, Mohammed A. Najmi, Kazuhiro Ohkawa, King Abdullah Univ. of Science and Technology (Saudi Arabia)
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The LEDs were obtained that the peak emission wavelength and FWHM were 665 nm and 67 nm at 20 mA, respectively. It exhibited a large blueshift of the EL peak wavelength from 691 nm at 5 mA to 631 nm at 100 mA. In this range, the blue-shifted value was 60 nm. Besides, we realized the single peak emission LEDs without an additional emission. We obtained a light output, forward voltage, and EQE of 0.07 mW, 2.45 V, and 0.19% at 20 mA, respectively. The LEDs exhibited the temperature stability of EL intensity and peak wavelength.
11686-75
Author(s): Zhe Zhuang, Daisuke Iida, Pavel Kirilenko, Martin Velazquez-Rizo, Kazuhiro Ohkawa, King Abdullah Univ. of Science and Technology (Saudi Arabia)
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Fabrication of indium tin oxide (ITO) was optimized for InGaN-based amber/red light-emitting diodes (LEDs). A radiofrequency sputtering reduced the sheet resistivity of ITO at low pressures, and a subsequent two-step annealing resulted in a low sheet resistivity (below 2×10-4 Ωcm) and high transmittance (over 98%) in the amber and red regions between 590 nm to 780 nm. Double ITO layers by sputtering could form an excellent ohmic contact with p-GaN. Application of the double ITO layers on amber and red LEDs enhanced light output power by 15.6% and 13.0%, respectively, compared to those using ITO by e-beam evaporation.
11686-76
Author(s): Zhe Zhuang, Daisuke Iida, Kazuhiro Ohkawa, King Abdullah Univ. of Science and Technology (Saudi Arabia)
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This work found larger red chips exhibited lower forward voltages due to their lower series resistance originated from the device area. Moreover, a larger chip resulted in a longer emission wavelength, narrower full-width at half maximum (FWHM), and higher EQE at high currents. These characteristics are beneficial for InGaN-based red LEDs. On the other hand, smaller chips had merits of a high characteristic temperature of 399K. This characteristic temperature is almost similar level with the world record in AlGaInP-based red LEDs, suggesting that InGaN-based red LEDs with small chip sizes are good candidates for temperature tolerant lighting applications.
11686-77
Author(s): Frank Mehnke, Zhiyu Xu, Theeradetch Detchprohm, Minkyu Cho, Shyh-Chiang Shen, Russell D. Dupuis, Georgia Institute of Technology (United States)
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III-Nitride laser diodes (LDs) emitting in the near ultraviolet spectral region enable applications such as chip-scale atomic clocks. However, LDs emitting near 369 nm suffer from material and heterostructure design challenges including stress induced layer cracking and p-type doping limitations. We will present a detailed study on the influence of Al mole fraction and thickness, the influence of a buried InGaN strain compensation layer, and the utilization of macro-patterned GaN/sapphire templates on the occurrence of surface cracks. Additionally, we investigated Mg back diffusion and GaN:Mg layer conductivity in dependence of growth temperature, V/III ratio, II/III ratio and TDD.
11686-80
Author(s): Yoshiya Miyamoto, Meijo Univ. (Japan); Naoki Sone, Meijo Univ. (Japan), Koito Manufacturing Co., Ltd. (Japan); Weifang Lu, Kazuma Ito, Renji Okuda, Meijo Univ. (Japan); Kazuyoshi Iida, Masaki Ohya, Koji Okuno, Koichi Mizutani, Toyoda Gosei Co., Ltd. (Japan), Meijo Univ. (Japan); Satoshi Kamiyama, Tetsuya Takeuchi, Motoaki Iwaya, Meijo Univ. (Japan); Isamu Akasaki, Meijo Univ. (Japan), Nagoya Univ. (Japan)
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A tunnel junction and a n-GaN cap layer grown on the multi-quantum shells (MQS) /nanowires are introduced to decrease the resistivity and optical loss. The selective-area growth of the MQS/nanowire core-shell structures on the template was performed by metalorganic vapour phase epitaxy (MOVPE). Further, the MQS structure was covered with the tunnel junction and the n-GaN cap layer. Here, the growth conditions of the n-GaN cap layer were systemically investigated. The effect of p-GaN shape on the morphology of grown n-GaN cap layer was also assessed.
11686-83
Author(s): Juhyeon Kim, Srinivasa Cheekati, Tuba Sarwar, Pei-Cheng Ku, Univ. of Michigan (United States)
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An optics-free spectrometer is demonstrated based on InGaN semiconductor photodiodes. The design is insensitive to the incident angle of light and delivers decent light absorption across the visible spectrum. In combination with compressive sensing algorithms, a high-performance spectrometer suitable for portable applications as well as sensing in harsh environments is shown.
Front Matter: Volume 11686
Conference Chair
Institute of Industrial Science, The Univ. of Tokyo (Japan)
Conference Chair
Virginia Commonwealth Univ. (United States)
Conference Chair
Technische Univ. Chemnitz (Germany)
Program Committee
Otto-von-Guericke-Univ. Magdeburg (Germany)
Program Committee
Institute of High Pressure Physics (Poland)
Program Committee
Raffaella Calarco
Paul-Drude-Institut für Festkörperelektronik (Germany)
Program Committee
National Sun Yat-Sen Univ. (Taiwan)
Program Committee
National Central Univ. (Taiwan)
Program Committee
Martin Feneberg
Otto-von-Guericke-Univ. Magdeburg (Germany)
Program Committee
Kyoto Univ. (Japan)
Program Committee
Lab. Charles Coulomb (France)
Program Committee
Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Program Committee
Yale Univ. (United States)
Program Committee
RIKEN (Japan)
Program Committee
National Chiao Tung Univ. (Taiwan)
Program Committee
Chih-Fang Huang
National Tsing Hua Univ. (Taiwan)
Program Committee
Motoaki Iwaya
Meijo Univ. (Japan)
Program Committee
Technische Univ. Berlin (Germany)
Program Committee
Elison Matioli
Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Program Committee
Taiyo Nippon Sanso Corp. (Japan)
Program Committee
Mie Univ. (Japan)
Program Committee
CEA-DRF (France)
Program Committee
Ritsumeikan Univ. (Japan)
Program Committee
Virginia Commonwealth Univ. (United States)
Program Committee
Institute of High Pressure Physics (Poland)
Program Committee
Univ. of Florida (United States)
Program Committee
Tae-Yeon Seong
Korea Univ. (Korea, Republic of)
Program Committee
Peking Univ. (China)
Program Committee
Hanyang Univ. (Korea, Republic of)
Program Committee
Maria Tchernycheva
Ctr. de Nanosciences et de Nanotechnologies (France)
Program Committee
Akio Wakejima
Nagoya Institute of Technology (Japan)
Program Committee
National Taiwan Univ. (Taiwan)
Program Committee
Seoul National Univ. (Korea, Republic of)