Foundation of Moldovan school of experimental semiconductor physics
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SIMASHKEVICH, Aleksey, ILIASENCO, Olga. Foundation of Moldovan school of experimental semiconductor physics. In: Materials Science and Condensed Matter Physics, Ed. 8-th Edition, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, Editia 8, pp. 26-27. ISBN 978-9975-9787-1-2.
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Materials Science and Condensed Matter Physics
Editia 8, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics"
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016

Foundation of Moldovan school of experimental semiconductor physics


Pag. 26-27

Simashkevich Aleksey, Iliasenco Olga
 
Institute of Applied Physics
 
Disponibil în IBN: 29 ianuarie 2019



Teza

The aim of this communication is a necessity, on the one hand, in this jubilee year for scientific institutions in the Republic of Moldova (RM), to recall the origin and roots of some fields and their ‘fathers-founders’ and, on the other, to fill gaps of some unknown or forgotten events, and, in some cases, to restore the "historical justice". This report presents data on the foundation of the scientific school of experimental semiconductor physics in the RM, which was organized on the base of the experimental physics department (EFD) of the Kishinev State University (KSU) in 1954 by professor Michail Kot, a talented physicist-experimenter [1]. M. V. Kot was a very energetic, ambitious, and courageous man. Thanks to his enthusiasm, perseverance, scientific intuition and leadership qualities, new educational and scientific laboratories were set up and a new scientific direction was launched without the necessary equipment and trained personnel. Professor M. Kot was very well aware of the importance of combining the educational process with research. During 14 year of professor’s M. Kot leadership in the department, the KSU trained more than 300 highly skilled specialists, 20 of its first disciples became doctors habilitate, including 7 members of the Academy of Sciences of Moldova. (A. Andriesh, D. Gitsu, M. Bologa, S. Radautsan. A. Simashkevich, A. Arushanov, I. Geru). All that has contributed to the fact that physics of semiconductors has become the leading branch of physical science in the country and continues to progress at the Moldova State University, the Institute of Applied Physics of the Academy of Sciences of Moldova, the Technical University of Moldova, the Tiraspol University.  If we would like to single out most important ideas and achievements of the students and researchers of the EFD of the KSU, the following should not be omitted. In those times, physics of semiconductors was a new area of science; however, one of the strong points of M. V. Kot was his physical intuition, which allowed him to identify the main lines of physics research before other scientists from leading scientific centers of the USSR did. In the fifties of the last century, the prevailing view among scientists in semiconductor physics was that reliable results that can form the base for the development of new physics mechanisms can be obtained only in bulk crystals with a perfect structure. Initially, at the EFD of the KSU, research was also carried out on bulk polycrystalline and single-crystalline samples, namely, CdSb (I. Andronic, E. Arushanov), ZnSb (I. Cretsu), and Sb 2S3 (S. Shutov)[2 - 4]. But M. V. Kot was persistently highlighting the importance of the study of thin semiconductor films. Thus, under his leadership, in 1954 the collaborators and students of his department started to work in the direction of preparing and investigating thin layers of groups II-VI and III-V semiconductor binary compounds. Those works were among the first in this field in the USSR and maybe even in the world. To prepare those layers, on the initiative of prof. Kot, the researchers applied the method for preparing and analyzing metallic alloys developed by S. A. Vekshinski (for which he received the USSR State Prize in 1946). In the case of applying that method for semiconductors, two different components of a binary compound are evaporated from two different sources on a heated substrate, where they form the desired compound. For example, the evaporation of cadmium and selenium on a glass substrate heated to 300°C makes it possible to obtain a pure CdSe layer because the excessive Cd and Se atoms could not be condensed on a heated substrate [5]. If the substrate is cold, a layer of a variable composition ranging from pure cadmium to pure selenium with a narrow cadmium selenide band is formed. Other II-VI compounds thin films have also been prepared and studied [6, 7]. If, using the above described method, binary compounds are evaporated instead of elementary components, then thin layers of variable compositions, consisting of a continuous series of solid solutions based on the used compounds, can be prepared. In this way, the synthesis of a large number of bulk samples to establish the dependence of the optical and electrical parameters of ternary solid solutions on their composition is not necessary [8]. Another important area of the research which began in 1961 on the initiative and under the guidance of M. V. Kot was the obtaining and investigating of semiconductor heterojunctions (HJs). The HJs based on II-VI compounds, such as CdSe-ZnTe, ZnSe-CdTe, and ZnSe-ZnTe, were prepared and studied. First results on the study of the electrical and photovoltaic properties of these HJs were published in 1964 [9], while in 1965 the injection electroluminescence was obtained in HJs formed by II-VI compounds for the first time [10]. It was the injection of minority carriers in the wide-band component of the HJ rather than a usual injection in a narrow-band component.  The main scientific results obtained by the collaborators of the EFD in the first 30 years of its activity can be briefly formulated as follows:- Developing the technology of growth of bulk crystals and thin layers of II-V, III-V and II-VI semiconductor compounds and solid solutions based on them.Developing the technology of obtaining HJs, Schottky diodes, MIS and SIS structures based on II-VI and III-V semiconductor compounds; determining the mechanism of a charge carriers transport in them and proposal respective band diagrams.- Determining the energy spectrum of impurities in II-VI semiconductor compounds and their solid solutions on the base of the role of these impurities in the formation of radiation spectra. - Obtaining, for the first time, injection electroluminescence in II-VI semiconductor materials.- Obtaining, for the first time, the electron-voltaic effect in II-VI type HJs.- Developing photovoltaic solar cells including tandem cells, based on II-VI compounds HJs. Photo-thermoplastic recording of optical information was another important research direction initiated in the 1960s in the KSU. The developments of those studies led to setting up of a specialized research laboratory of photo-thermoplastic recording. Some comments now. Unfortunately, the method of thin film deposition and certain other results, e.g., the obtaining and investigating of HJs, were not patented at that time and/or published only in Russian. That is why, a few years later, another researcher, out of ignorance, and might be even of an unfair intention, offered it with slight modifications. For example, the method of thin film deposition, elaborated at the KSU, nowadays is universally accepted under the title "Three-temperature method” or “Gunter method” [11]. It is also not clear why there is a long-time ignorance of the elaboration and investigation of the HJs based on II-VI materials, although these results were presented at the first international conference on the HJs in Budapest in 1970, in the presence of leading researchers in this area [12]. [1] A. Simashkevich, O.Iliasenco. Mold. Journ. Phys. Sciences, 13, 3-4 (2014), 133-137. [2] I.К. Andronik, М.V. Коt, I.V. Cretsu. Uchen. Zapiski КGU, 49, (1961), 105-111  [3] I.K.Andronik, E.K.Arushanov, O.V.Emelyanenko, D.N.Nasledov, Phys.Stat Sol.27, 1, (1968), 45-49.  [4] M.V.Kot, S.D. Shutov. Trudy po fizike poluprovodnikov. KGU, 1 , (1962), 47.[5] А. V. Simashkevich and S. I. Slutu, Uchen. Zapiski КGU, 29, (1957),153.[6] М. V. Коt, and А. V. Simashkevich, Izv. Vyssh. Uchebn. Zaved., Fiz. 3, (1959), 125.[7] М. V. Коt and А. V. Simashkevich, Izv. Akad. Nauk SSSR, Ser. Fiz. 28, (1964), 1064.[8] М. V. Коt, V. G. Тyrziu, А. V. Simashkevich, Yu. E. Maronchuk, and V. A. Mshenskyi, Fiz. Tverd. Tela 4, (1962), 1535.[9] М. V. Коt, О. Ya. Коrshak, А. V. Simashkevich А. А. Тоdorov, D. А. Sherban, and А. Е. Tsurcan, Fizika p-n Perekhodov, Riga, 1966, 261.[10] М. V. Коt, L. М. Panasyuc, А. V. Simashkevich, А. Е. Tsurcan, and D. А. Sherban, Fiz. Tverd. Tela 7, (1965), 1244.[11] K.G Gunter. The Use of Thin Films in Physical Investigations, Ed. J.C. Anderson, Acad.Press. London, (1966), 213. [12] I.K.Andronik, P.A. Gashin., I.V. Dementiev, G.P. Listunov, L.M. Panasiuk , A.V. Simashkevich, D.A. Sherban. Proc.of  Int. Conf. on Phys. Chem. of Semiconductor Heterojunctions and Layer Structures, Budapest, 2, (1970), 211.