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III-nitride based microcavities (MCs) appear as one of the most promising candidates for the realization of room temperature (RT) polariton laser diodes. The present work focuses on the properties of low In content InGaN/GaN multiple quantum wells (MQWs) in terms of inhomogeneous broadening, exciton localization energy, and plastic strain relaxation. For a small number of such QWs, an inhomogeneous line broadening of 41 meV is reported, which is compatible with strong coupling regime requirements. By contrast when considering an InGaN/GaN MQW set, a high density of defects is reported, which is ascribed to plastic strain relaxation. From the evolution of the inhomogeneous line broadening as a function of the number of QWs probed by microphotoluminescence measurements, it is concluded that for the realization of polariton light-emitting devices the QW number should not go beyond 30 for MC structures grown on FS-GaN substrate relying on InGaN/GaN QWs with an indium content similar to 12-15% and thicknesses of 1.5-2 nm/3 nm for the wells and the barriers, respectively. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

We propose to use lattice-matched AlInN/GaN to replace the Al(Ga)N/GaN material system for III-nitride Bragg reflectors, despite the poor material quality of AlInN reported until very recently. We report an improvement of AlInN material that allowed for successful fabrication of a microcavity light emitting diode, a distributed Bragg reflector with 99.4% reflectivity and microcavities with a quality factor over 800. These results establish state-of-the-art values for III-nitrides, and announce the future importance of AlInN in GaN-based optoelectronics. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stimulated polariton scattering in semiconductor microcavities is reported. The phenomena arise from the bosonic character of the coupled exciton-photon modes of the system. The ability to manipulate and control the polariton dispersions in microcavities is shown to be a key factor underlying the new observations. The potential of such phenomena to form the basis of a new type of coherent light source ("polariton" lasers) and highly efficient optical parametric oscillators is discussed.

We report on a clear experimental demonstration of the presence of biexciton recombination in high quality GaN/AlGaN quantum wells, thus opening the way to relevant improvements of the performances of GaN based devices. The samples have been grown by metalorganic vapor phase epitaxy optimizing the deposition conditions to strongly reduce the Al fluctuations in the barriers. This leads to a photoluminescence broadening of only 5 meV at a temperature of 10 K for an Al content in the barriers of 5%. The biexciton binding energy if found to be of the order of 9 meV. The recombination kinetics show that the exciton and biexciton components are not thermalized at low temperature allowing to extract the intrinsic lifetimes of the two components. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The 5th International Workshop on Nitride Semiconductors (IWN 2008) took place from 6–10 October 2008 at the Montreux Music and Convention Centre (2M2C) in Montreux, Switzerland. The event, organized by the Ecole Polytechnique Federale de Lausanne (EPFL), continues the series of previous nitride workshops which started in Nagoya, Japan (IWN 2000), followed by meetings in Aachen, Germany (IWN 2002), Pittsburgh, USA (IWN 2004) and Kyoto, Japan (IWN 2006). The main areas of research on III-nitrides were presented during full day plenary sessions on the first two days and on the closing day of the meeting, followed by seven parallel workshop (WS) sessions during the third and fourth day of the meeting, each workshop being organized around a specific aspect of current interest: Substrates for nitride epitaxy (WS1), Challenging materials issues: InN and high In-content alloys (WS2a), AlN and high Al-content alloys (WS2b), Non-polar epitaxy (WS2c), Nanostructures (WS3), Novel physical concepts and devices (WS4), Optoelectronics-1: materials and physics (WS5), Optoelectronics-2: technology and devices (WS6), and Electronic devices (WS7). Finally, the workshop organizers presented the main conclusions from the individual workshops during the closing plenary sessions on the final day of the meeting. During the meeting a total of 35 invited lectures were given, divided between the plenary sessions and workshop sessions. A total of 498 contributed papers were presented, selected by the Program Committee out of 623 (regular) and 25 (late) abstracts submitted. Of these, 12 regular and late papers of major interest were presented during the plenary sessions, 255 were presented during the parallel workshop sessions, and 236 were presented as posters. The International Workshop on Nitride Semiconductors and the International Conference on Nitride Semiconductors, held in alternating years, constitute the major conferences devoted to the science and technology of III-nitride semiconductor materials and devices, covering materials growth and processing, physics of electronic and optical processes, and advanced electronic and photonic devices. The materials covered include all III-nitride compounds and heterostructures. The meeting attracted 710 participants, reflecting the large interest in the field driven by the huge application potential of the nitride materials family, probably second only to the silicon field. Aside from visible to near UV light emitting diodes (LEDs) and lasers, which are currently already making major inroads in the laser and general lighting markets, future developments in high-power high-speed electronics, high voltage rectifiers, and industrial sensors promise to have a large impact and are expected to establish new performance limits in the semiconductor field. The interest was also manifested by the presence of 20 companies participating in the industrial exhibit. The present proceedings, published in Phys. Status Solidi A 206(6), Phys. Status Solidi B 246(6) and Phys. Status Solidi C 6(S2) (2009), contain 221 papers, including 12 invited papers, which cover the entire range of topics discussed during the technical sessions including contributions on hot topics such as non-polar and semi-polar III-nitride epilayers and heterostructures, UV and green LEDs, the origin of the efficiency droop of LEDs, and the performance and reliability of high electron mobility transistors to cite only a few examples. Raphael Butte, as Proceedings Editor, wishes to warmly thank the numerous referees, who contributed through their detailed reports to the completion of this volume, as well as the editorial and technical staff of physica status solidi (with special thanks addressed to Stefan Hildebrandt and Julia Huebner) for their diligence, their availability, and their advice, which greatly helped completing the reviewing process in seven months. Finally we would like to thank the members of the IWN International Advisory Committee for their participation in the selection of the invited speakers and for their general support and encouragement, and the members of the Program Committee, and in particular the organizers of the topical workshops, for their efforts in selecting and reviewing the papers and in organizing the workshop sessions. Our thanks also go to the institutional and industrial sponsors – without their help the workshop would not have been possible –, to the technical staff of the 2M2C and to the EPFL staff members and students who made this meeting a success. In particular, we would like to mention the contributions of Carole Preciado, Aline Gruaz, Virginie Ledouble, and Oana Chiper for the administrative and local arrangements, of Jelena Ristic and Denis Martin for organizing the industrial exhibit, and of Dobri Simeonov for the design of the IWN 2008 website and the on-line management of the registrations, abstract submission, and program guide (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the dependence on temperature of the homogeneous and inhomogeneous broadening of the fundamental transition of single polar GaN/AlN quantum dots (QDs). Stranski-Krastanov QDs have been grown by molecular beam epitaxy using NH3 as a nitrogen source, with a very low surface density. Low temperature (LT) microphotoluminescence measurements have been performed on 200 nm wide mesas in order to isolate the luminescence of single QDs. The linewidth is found to vary from 590 mu eV at 4 K up to 1350 mu eV at 65 K in a dot of 6 monolayer height. Though the LT linewidth is still dominated by spectral diffusion, the temperature dependent broadening up to 50 K is mainly accounted for by interactions between excitons and acoustic phonons through a coupling coefficient value nearly two orders of magnitude larger than its counterpart in InAs QDs. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Intersubband (lSB) optical absorption in different nitride-based heterostructures grown by metal-organic chemical vapour deposition (MOCVD) is reported. The role of indium in AlInN/GaN multi-quantum wells (MQWs) is investigated. At high concentration (15%) AlInN is quasi lattice-matched to GaN and no cracks appear in the structure. At very low indium concentration (similar to 2%) the material quality is improved without decreasing the ISB transition wavelength with respect to the case of indium-free structures. Different mechanisms of strain relaxation in pure and 2% indium-doped AlN/GaN MQW structures are also investigated. ISB transition wavelengths of 2 urn for AlN/GaN MQWs, and 3 mu n for AlInN/GaN MQWs with 15% of In are achieved. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.