Physical, Technical and Computer Sciences Institute of Yuriy Fedcovich Chernivtsi National University

Department of Optoelectronics

History of the department

Department of Optoelectronics, founded in Chernivtsi University in 1984, became the successor to the Department of Experimental Physics – among the oldest natural sciences departments of the University that existed since its founding in 1875. For decades, the Department of Experimental Physics traditionally provided instruction of General Physics course. Only in the 1960s, the Department formed several groups of highly qualified tutors and researchers investigating  common research subjects. Strengthening the research and improving logistical support led to organization of new experimental Physics departments, including the Department of Optics and the Department of Physics, which were later included in the Engineering Department.

In the late 1950s, the Head of Department Professor I.K. Vereshchagin initiated the research in luminescence and photoelectronics, which have gained extensive development and soon grew into a powerful scientific direction of the department.

The Doctoral Thesis of I. Vereshchagin was dedicated to electroluminescence of crystals – a phenomenon that is the basis of modern light sources, which are the LEDs and semiconductor lasers. The monograph by I. Vereshchagin published in "Nauka" (Moscow) was devoted to the problem of direct conversion of electrical energy into light. Subsequently, in collaboration with L.A. Kosyachenko the monograph and textbook were published in Publishing Houses "Energoatomizdat" and "Visshaya Shkola" (Moscow). The new specialization of optoelectronics was introduced for students, the Graduate School was started. From 1970 to 2007 the Department of Experimental Physics (since 1984 – Optoelectronics Department) was headed by Prof. L.A. Kosyachenko.

In his doctoral thesis (1982) the results of a comprehensive study of pre-breakdown electroluminescence of semiconductor structures – a specific type of optical radiation that is closely associated with a number of complicated physical processes – were summarized. In this paper the important features of scattering mechanisms of "hot" electrons, the dynamics of its acceleration by the strong electric field, energy loss, the abnormal formation of the distribution function of electrons and holes were determined. The necessary parameters of semiconductors were found, the main characteristics of the phenomenon were quantitatively described, the reasonable physical model of light source that is perspective from the viewpoint of practical application was substantiated. The achievements of the scientists of Optoelectronics Department I.T. Drapak , I.V. Solonchuk , V.V.Guts, V.P. Mahniy , B.M. Sobischanskiy, M.M.Slyotov, V.E. Baranyuk, I.S. Kabanova, V.V. Melnik and other researchers widely recognized both in Ukraine and abroad are sufficient. The development of a new class of sources and photodetectors of optical radiation were implemented by research institutions in Kyiv, Moscow, St. Petersburg, Kazan, Yerevan, Chernivtsi. The results of the study of "hot" electrons, nonequilibrium and contact phenomena in semiconductors have been added to the prestigious international conferences, which were held in Germany, Finland, USA, Japan, France, England, were published in international journals with highest rating. Under the supervision of Prof.L.A. Kosyachenko 15 Ph.D. Theses were defended.

The study of physics of LEDs among others has resulted in the development of light sources with electrically controlled glow color (together with the Department of Construction Bureau "Phonon" (supervisor ‑ prof. Kosyachenko L.A.). Customized and funded by O. Antonov Aviation Scientific-Technical Complex and S.P. Korolev Rocket Space Corporation "Energiya" the displays for the aircraft "Ruslan" and simulatosr for astronauts have been developed. According to the order of the S.I. Vavilov State Optical Institute the LED-sources of reference radiation emitters (class A, 2856 K) were developed.

During 1990s the close scientific and technical cooperation with the Institute of Optoelectronics of China in the field of development of photodiodes for "transparency windows" in the atmosphere of 8-14 microns have been established and a bilateral agreement on joint research has been signed. There have been numerous mutual visits. Prof. L.A. Kosyachenko made 5 visits (2-3 weeks each with full covering of all expenses by the inviting party) at the Institute of Optoelectronics (China), equipped with modern facilities, allowing implementing the necessary technology and measurements. Ph.D. Thesis of Sung Veyhuo, the employee of the Institute of Optoelectronics, was defended in Chernivtsi University. Numerous visits of Prof. L.A. Kosyachenko in the universities of Berlin, Bremen, Nürnberg, Max Planck Institute (Germany), Xian (China), participation in international conferences in West Berlin, Potsdam, Oxford, Milan, Okayama also have contributed to the international cooperation of Optoelectronics Department. Prof. Kosyachenko received a scholarship from the German Academic Exchange Service DAAD and worked during the semester at the University of Berlin.

Since 2007 Prof. Makhniy V.P. has been the Head of Optoelectronics Department.

His doctoral thesis (1992) was devoted to the study of physical processes in diode structures based on wide-gap semiconductors A2B6.The thesis have founded technological basis of production of rectifying structures of various types (surface-barrier diodes, MDS structures, p-n-homo- and hetero-junctions) with reproducible and stable over the time parameters and characteristics. A number of optoelectronic devices have been made on the basis of the thesis. The paper presents physical models that enabled to adequately explain the features of generation-recombination, tunneling and avalanche processes with regard to the main parameters of wide-gap semiconductor and diode structure, deep levels and dispersion law in the forbidden zone. Under the supervision of Prof. V.P.Mahniy 1 doctoral and 10 Ph.D. theses were defended.

In 2010 Associate Professor M.M. Slyotov defended his doctoral thesis "Mechanisms of luminescence in diffusion layers of II-VI wide-gap semiconductors", dedicated to the  study of the properties of diffusion layers and heterostructures of II-VI compounds; the establishment of technological regimes of obtaining hole conductivity and studying the effect of hetero- and isovalent impurities on the properties of layers; methods of λ modulation in the manufacture of measuring complex (which allows to explore the different nature of the generation-recombination processes of optical absorption, reflection and luminescence); to elucidate the mechanisms of radiative recombination; to produce laboratory samples of high-temperature phosphors, photodetectors and modulators of fluorescent radiation on the layers and heterostructures.

Over the last 15-20 years more than 20 Ph.D. theses on the subject of research of the department have been defended, 5-6 theses being performed by postgraduate students are now on the stage of completion. Assoc. Prof. V.M. Sklyarchuk and O.L. Maslyanchuk work successfully on their doctoral theses. High scientific potential is providing the appropriate level of the department graduates, the number of whom has grown to more than 300 for the last 20 years.

Recently, the scientific work of Optoelectronics Department has been focused on solving the technological problems of semiconductor materials and devices with enhanced functionality. Particular attention is paid to the development and research detectors of electromagnetic radiation of different spectral ranges and solar cells.

Optoelectronics Department maintains close scientific cooperation with the other departments of the University: Departments of Physics of Semiconductors and Nanostructures, Electronics and Power Engineering, Solid State Physics, Thermoelectricity, Inorganic Chemistry as well as many scientific and higher educational institutions of Ukraine, including Kyivv, Odesa and Lviv Universities, Lviv Polytechnic National University, Institute of Physics and Institute of Semiconductor Physics, National Academy of Sciences, Kharkiv Institute for Single Crystals, Kharkiv National University, as well as institutions from abroad: Lebedev Physical Institute (Moscow), Ioffe Physico-Technical Institute (St. Petersburg), Berlin Institute of Technology, the Max Planck Institute (Stuttgart, Germany), University of Milan, Institute of Optoelectronics of China, Northwest University of China (China), Belarusian State University (Belarus), the Mexican National University (Mexico City, Mexico), University of Valencia (Spain). This is confirmed by numerous publications in scientific journals and talks presented at Ukrainian and international conferences. Prof. Kosyachenko was invited to make presentations and lectures at Max Planck Institute, Universities of Bremen and Nuremberg Germany. The joint research with the world famous Berlin Institute of Technology, Loyan Institute of Optoelectronics (China), University of Valencia (Spain), the Mexican National University, Northwestern (China), Technological Institute of Chalkis (Greece), National Centre for Scientific Research "Demokritos" (Greece), Albert Ludwig University (Germany), Autonomous University of Madrid (Spain), Technical University of Riga (Latvia), Research Institute of Electronics Shizuoka University (Japan).

In 2008, the Optoelectronics Department received a proposal to take part in the development of radiation control at customs in Europe. Chernivtsi University entered a consortium to implement a 3-year project, which was also attended by research groups from 6 countries in Europe, the Institute of Electronics Shizuoka University (Japan), Institute of Semiconductor Physics National Academy of Sciences and Chernivtsi University. The research team from Chernivtsi University was requested to provide scientific support in the development of tools, funding totaled about 1.5 million UAH. In the by-project implementation the models of devices that allow instant determining the location and type of radiation source in a wide range of energy quanta were developed. One of the partners in the consortium (Finnish company Ajat Co.) produced these detectors.

In the view of experts the work of Chernivtsi University group in the project was so successful that the European Commission financially supports scientific research of the department after the official completion of the work. As the development of the project a new international project of the European Commission was started. The review of the project is delayed due to the financial crisis. Optoelectronics department also invited to participate in the NATO project to establish a network of detectors to identify and determine the localization of radioactive sources.

Participation in such projects increases the scientific work of students and young scientists of the department. Presentations of our students at scientific conferences are always among the best. During the past 10 years graduate student and post-graduate students are involved (with financial support) in school-conference of young scientists on semiconductor physics taking place in Poland. Research Associate E.V. Grushko has worked in the laboratories of the Institute of Electronics in Japan three times for three months, twice – at the Institute of Nuclear Physics in Greece, and has won a grant of the President of Ukraine, as well as a grant of the Ministry of Education of Ukraine for 6-month training at one of the leading universities in Europe (Albert Ludwig University, Frieburg, Germany and Autonomous University of Madrid, Spain).

The research conducted at the Optoelectronics Department shows that thin-film solar cells on CdTe production rates are much higher than those of silicon counterparts, and the technology for CdTe solar modules is easier and cheaper. Achievements of the Optoelectronics Department in this subject are knows in Ukraine and abroad. The review articles were published in "Ukrainian Journal of Physics", International Journal «Materials for Renewable and Sustainable Energy». In recent years two Ukrainian-Belarusian joint projects and Ukrainian-Russian project have been successfully completed. Close scientific and technical cooperation with the Research Centre "Energy" (Mexico), Institute of Energy Conversion (USA), University of Osaka (Japan) and other institutions was established.

The invitation of Prof. L.A. Kosyachenko to be an editor of a four-volume book «Solar Cells", which was published by «InTech Publishers» (Vienna) was another internationally recognized achievement of Optoelectronics Department. The book is dedicated to optoelectronic devices that convert the energy of sunlight directly into electricity without harming the environment. The book includes chapters written by the authors from 41 countries, including the well-known scientists and recognized experts in the field of photovoltaic. The introductory chapter "Thin-film technology – mainstream of solar energy" (38 pages book format) was written by Prof. L.A. Kosyachenko. It was proved that using thin-film solar cells can transform existing energy system into ecologically clean one and, thus, stop global warming.

Educational process is an important part of the activities of the Department of Optoelectronics. For all students specializing in "physics" department provides training in three subfields of physics:

• optics;

• atomic and nuclear physics phenomena;

• the basics of electrical engineering and electronics.

Disciplines of specialization and laboratory practice are covering all the major sections of optoelectronics:

• optical, photoelectric and luminescen tphenomena in condensed matter;

• electronic processes in crystals with an emphasis on the needs of functional electronics;

• contact phenomena, especially in homo- and hetero- graded-gap semiconductor and other structures;

• semiconductor optoelectronics, including laser and light emitting diodes, photodetectors, optocouplers, display devices;

• Optical methods of processing;

• integrated and fiber optics;

• optoelectronic technology.

The department provides the postgraduate program that prepares highly skilled professionals in Physics of semiconductors and dielectrics for the needs of the university, the region and other countries.