Special issue in honour of Prof. Marc Ilegems

It is a real pleasure and honor for me to write this preface to the festschrift in honor of Marc Ilegems on the occasion of his 65th birthday. As all of his collaborators, I have always had a great pleasure to work with Marc and appreciated a lot his competence, dedication and subtlety in all matters. It has been very difficult, among the amount of work carried out by Marc throughout his carrier, to choose a topic that would allow for a self‐contained book. It would have been possible for example to center the book on GaN based structures and devices. I however used my privilege, as a guest editor, to choose the field where my own collaboration with the group of Marc has been the most fruitful, the field of semiconductor microcavities. Marc Ilegems was born in Antwerp, Belgium, on April 19th 1940. He studied at the Ecole polytechnique of the Free University of Brussels (ULB) where he graduated in July 1963 with “ Great Distinction ” and got a degree in Electrical Engineering. He obtained further a Certificate in Telecommunications in July 1964. From October 1963 to September 1964, and, after an interruption for military service, from January 1965 to August 1965, he was employed as a research assistant in the Laboratory for Electronics of the University of Brussels, working on parametric frequency division using nonlinear capacitive elements. He was awarded a fellowship from the Fullbright Foundation in May 1966 and enrolled in the Master's degree program at Stanford University, California, from September 1966 to June 1967. In July 1967 he started his doctoral research under Professor Gerald L. Pearson in the Electrical Engineering Department, working on the growth by liquid phase epitaxy of AlGaAs mixed crystals and on the study of the infrared reflectance of Al x Ga 1– x As crystals. The results of this work 1, 2, published in 1969 and 1970, were amongst the very first publications on this new and very important semiconducting material. His results have been validated by numerous later studies and publications on the subject. In September 1969, he has been enrolled as a Member of Technical Staff at the Solid State Electronics Research Laboratory, Bell Laboratories, Murray Hill, in the group directed at the time by Dr. Morton B. Panish. Over the time period 1969–1972 he worked on the study of the liquid–solid phase diagrams of ternary and quaternary semiconducting compounds in collaboration with M. B. Panish and A. Jordan 3, 4. This was both experimental and modeling work. In parallel, he worked on the vapor phase growth of GaP, and, following the publication of the first paper by J. Pankove and coworkers at the RCA Laboratories on the growth of GaN, on the vapor phase epitaxy of gallium‐nitride compounds 5. The work on the nitrides, in collaboration essentially with R. Dingle, D. Sell and H. Montgomery, led to the first detailed papers on the luminescent properties 6 and the bandstructure of GaN 7 paving the way to the present use of GaN for blue light emitters. The first temperature dependent electrical characterizations of GaN epitaxial layers published in 1972 8, reported mobility values of 440 and 780 cm 2 /Vs at room temperature and 55 K, respectively, values which have stood as absolute records in the literature for over 20 years. Because of the inability to achieve p‐type doping in GaN at the time, the emphasis on the work in the 1972 to 1977 period shifted to the growth and characterization of GaAs and AlGaAs materials by the then new technique of molecular beam epitaxy (MBE) initiated by Al Cho of the same laboratory. Significant results from this work were the first demonstration of the use of beryllium as a p‐type dopant in GaAs 9 as it is still used worldwide today, the first demonstration of a load‐lock system for MBE growth 10, allowing for the first time to obtain AlGaAs layers with high luminescent efficiencies, the first demonstration of selective area growth by MBE using shadow masks 11, and the first demonstration, with J. P. Van der Ziel, of the growth of monolithic GaAs/AlAs Bragg mirrors 12, which six years later have become the key elements in the development of vertical cavity surface emitting lasers (VCSELs) and opened up the field of semiconductor planar microcavities for quantum optics. In September 1977, Marc Ilegems joined the Ecole Polytechnique Fédérale de Lausanne (EPFL) as an associate Professor and Director of the newly created Interdepartmental Institute for Microelectronics, with the dual mission to establish a physics and technology oriented microelectronics curriculum for students in Lausanne and to develop a research program complementary to and/or in cooperation with the existing Microelectronics R&D programs developed in the Centre Electronique Horloger in Neuchâtel. In 1988, the Interdepartmental Institute for Microelectronics merged with the Optoelectronics Laboratory headed by Prof. F. K. Reinhart to form the new Institute for Micro and Opto‐electronics. Marc Ilegems has been the director of this institute for 10 years, from 1988 till 1998 before he became the head of the physics department. The direction of Marc Ilegems has always been smooth and very efficient. From 1998 to 2000, M. Ilegems served as the Head of the Department of Physics at EPFL, again with great competence and dedication. He then has taken the responsibility of the Swiss National Center of Competence in Research in Quantum Photonics, which groups together the competencies of the leading laboratories in Switzerland in the field of photonics. During his time at EPFL the research carried out by the group of Marc Ilegems has first concentrated on the field of silicon technology with a large program around the modeling and optimization of short channel length CMOS transistors, hot electron injection, trapping and breakdown in non‐volatile electrically programmable memories, and low frequency noise measurements as a tool to study degradation in MOSFETs. Marc has also launched a research in III–V materials and devices initially centered around the application of the molecular beam (MBE) and chemical beam epitaxy (CBE) techniques, with activities directed, on the one hand, towards materials growth and characterization, and on the other hand to the realization and study of a wide variety of electronic and optoelectronic devices. Examples of the work carried out, in general in the framework of doctoral thesis projects, include: – study of doping, oxygen incorporation, and deep level defects in GaAs and AlGaAs layers and high electron mobility transistors (HEMTs) using transient capacitance and low frequency noise measurements, – development of the CBE and selective area growth techniques for GaInAs and GaInAsP‐based quantum well structures and diode lasers 13, – realization and study of high speed GaAs and GaInAs‐based photodetectors at 850 to 1300 nm wavelengths, 2D electron gas high electron mobility transistors (HEMTs) based on pseudomorphic GaInAs on GaAs or lattice matched GaInAs on InP substrates, and GaAs‐based quantum Hall resistance standards, – realization of high finesse semiconductor microcavities with distributed Bragg reflectors 14 and study of their luminescent properties in the cavity‐polariton regime, demonstration of room temperature cavity polaritons 15, – development of high brightness microcavity light emitting diodes 16, – study of coupled cavities and demonstration of dual‐wavelength lasing in coupled microcavities 17. Starting in 1997, the research interest partially shifted to the growth and study of nitride‐based wide bandgap materials and devices. Research topics included the growth of thick GaN layers by hydride vapor phase epitaxy to be used as pseudo‐substrates, and the achievement of reduced defect densities by using epitaxial lateral overgrowth 18, the growth by metal organic vapor phase epitaxy of GaN‐based light emitting diodes and diode lasers, and the development of high reflectance lattice‐matched AlInN/GaN distributed Bragg mirrors 19 as an alternative to the commonly used highly strained GaN/AlN mirrors, and the demonstration of the first high quality factor AlInN/GaN monolithic microcavities 20. This research field will be continued in the next phase of the Quantum Photonics NCCR by Nicolas Grandjean. In addition to the projects described above, Marc Ilegems initiated programs on two‐ dimensional photonic crystal devices for integrated optoelectronics as well as programs on self‐organized quantum dot growth for long wavelength lasers on GaAs, research fields that will be continued respectively by Romuald Houdré and by Andrea Fiore. The research in Marc Ilegems' laboratory is carried out in close collaboration with groups at the EPF Lausanne, the ETH Zürich, the Universities of Neuchâtel and Geneva, as well as with many laboratories worldwide. The work has been supported by the Swiss National Science Foundation and by several European Community research programs such as SMILED (microcavity light emitting diodes), MONOLITH (monolithic integration of GaAs light emitters on silicon), GSQ (gallium arsenide quantum dot lasers), VISTA (vertical cavity lasers for information society applications), PCIC (photonic crystal integrated circuits), FUNFOX (functional photonic crystal devices for optical networks), LAQUANI (nitride semiconductors for diode light emitters and lasers), EURONIM (European sources for nitride materials) and ePIXnet (European network on photonic integration). The laboratory has also strongly benefitted from a collaborative research program with the Central Research Laboratory of Thomson CSF in France during the 1987 to 1993 period. The research carried out at EPFL within his research group resulted in over 230 refereed publications and more than 30 doctoral theses. Marc has contributed with great enthusiasm to teaching in EPFL: courses he has given include physics and technology of semiconductor electrical and optical devices, and introductory quantum physics, given to 2nd to 4th year students of the Physics, Electrical Engineering and Microtechnology departments. One of the major activities of Marc Ilegems over the years has been his commitment to the managing of science at the Swiss level. Marc Ilegems first served as a director of the Swiss National Program on Micro and Optoelectronics, funded by the Swiss National Science Foundation, over the years 1983–90. He then served as a director of the Swiss Priority Research Program in OPTICS, years 1993 to 1999, funded by the Board of the Conseil des Ecoles Polytechniques Fédérales. Eventually, Marc Ilegems became the Director of the Swiss National Center of Competence in Research in Quantum Photonics, which groups together the expertise of the leading laboratories in Switzerland in the field of photonics. Meanwhile, he served as a member on the scientific council of the Centre Suisse d'Electronique et de Microtechnique (Neuchâtel), the Paul Scherrer Institute (Zurich), the Centre National d'Etudes des Télécommunications (Paris), the Laboratoire d'Electronique et de Systèmes (Ecole Centrale de Lyon), and the Ferdinand Braun Institute (Berlin), and as an expert for the research programs of the European Community and of the Deutsche Forschungsgemeinschaft. Marc Ilegems also contributed to the organization of several scientific conferences and meetings. He chaired the 21st International Symposium on Compound Semiconductors (ISCS 2001, Lausanne), the Monte Verita Summer Schools on Quantum Dot Lasers (2004), Two‐dimensional Photonic Crystals (2002) and Microcavity Light Emitters (1998 and 2000), the 6th International Conference on Chemical Beam Epitaxy and Related Techniques (ICCBE 1997, Montreux), the 21st European Solid State Device Research Conference (ESSDERC 1991, Montreux), the 4th International Workshop on Compound Semiconductor Devices and Integrated Circuits (Lugano, 1989), and the 3rd European Workshop on Molecular Beam Epitaxy (Les Diablerets, 1987). He presently is the chairman of the Steering Committee of the International Symposium on Compound Semiconductors. In recognition of his contributions to III–V semiconductor materials and device research, M. Ilegems was awarded a honorary doctorate by the University of Toulouse in 1999.