Оптимизация методов импульсной лазерной обработки кристаллов Cd(Me)Te и Ga(As, Se, N)

Аннотация

Topicality and necessity of the thesis. Upon production of the modified structure with improved parameters, a good choice of technologies and methods of processing of semiconductors and structures based on them is important. For example, the use of pulse laser treatment of crystals and semiconductor structures can control the mechanisms and laws of diffusion. Moreover, nanosecond laser irradiation of binary and ternary solid solutions of semiconductor crystals makes it possible to receive an acoustic response and shock wave, to define the temperature, pressure and impurities distribution, providing new photovoltaic properties of semiconductor surfaces. The use of gallium nitride allows learning the correlation of acoustic emission and changes of luminescent and electrical characteristics in the LED structures when passing current. Research work carried out in the above directions indicate the relevance of the topic of the dissertation. Relevant research priority' areas of science and developing technologies of the Republic. This thesis performed in accordance with the priority areas of science and technology of the Republic of Uzbekistan. See section III «Energetics, energy and resource economy, transport, mechanical engineering and instrumentation; the development of modem electronics, microelectronics, photonics, electronic instrument engineering.” A review of international research on the topic of the thesis1. Research of laser irradiation to improve technology and optimize the parameters of X-ray and gamma-ray detectors conducted in leading scientific centers, including National Center for Biotechnology Information (USA) and Shizuoka University (Japan), Tashkent State Technical University, and Samarkand State University. Problem development status. The decisions of a problem of controllable transformation of structure require (demand) superficial layers Cd (Me) Те and Ga (As, Se, N) with the help eiioeunii of laser processing for effective management of their photo-electric, electrical, luminescent and optical properties. Relevance of the dissertation research to the plans of scientific-research works. The dissertation research is carried out within the framework of the plan of scientific research for the project P-18.52 "Exploring the technology of obtaining silicon wafers for intended solar cells", Nukus State Pedagogical Institute, and on the basis of collaboration between the V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine on the theme № 2.1.1/17 "Development and creation the acoustic-emission rapid method for monitoring and predicting the reliability of semiconductor materials and structures" for 2008-2017 years and Karakalpak State University. The aim of research work is process optimization of nanosecond laser processing of semiconductor crystals of Cd (Me) Те and Ga (As, Se, N) and the study defect formation, diffusion, shock-wave process, acoustic emission and nonlinear optical effects there. The subject of research - the compound semiconductors cd(Me)Te, Ga(As, Se,N) under pulse laser treatment. The object of study - the processes of defect formation, mass transfer, the shock wave, the acoustic emission under nanosecond laser irradiation of Cd (Me) Те, Ga (As, Se, N). Methods of the research: Raman scattering, photoconductivity, photoluminescence, electroluminescence, optical transmission, the two-photon absorption, induced absorption and bleaching, Auger analysis, stratified and selective etching, methods for studying the surface morphology, the currentvoltage, voltage-farad characteristics, acoustic emission method, theoretical calculations. Scientific novelty' of the research work it is shown that the treatment of high-resistance crystals of CdTe, CdZnTe by nano-second pulses of a ruby laser makes it possible to improve the state of the surface; The conditions for increasing the sensitivity and reducing the rate of surface recombination, as well as changes in the spectral range of photoluminescence and photoconductivity, are found; an acoustoemission method for determining the melting thresholds of semiconductor crystals, in particular, CdTe and GaAs, is developed from the change in the amplitude and energy of acoustic radiation during; a method for fabricating a Te-CdTe structure with the electronic memory switching feature by nanosecond laser irradiation of CdTe is proposed; it is established that on the basis of acoustic emission mechanisms it is possible to determine the melting threshold of single crystals of semiconductors under pulsed laser irradiation of CdTe and GaAs; regularities and methods of optimization by pulsed laser surface treatment of semiconductors for use in the technology of laser processing of CdTe, TP based on it, GaAs, GaSe. Practical results ot research work It has been shown that treatment of high impedance crystal CdTe, cdxZn,^Te with x=o,i и x=0,04 under nanosecond ruby laser pulses can improve the condition of the surface: to increase the sensitivity and to reduce the surface recombination velocity, as well as change the spectral range of photoluminescence and photoconductivity. It was proposed a method for the manufacture of Te-CdTe structure with electronic switching property with memory by nanosecond laser irradiation of CdTe. .Discovered patterns and the optimization of method PLI for semiconductorsurface can be used in laser processing technology of CdTe, solid solution based on it, as well as GaAs, GaSe. Authenticity of the obtained results is is confirmed by the use of modem scientific and technological methods, standard and proven monitoring techniques. The results and conclusions are justified on physical performances based on theoretical and experimental data. The reliability of the experimental data provided by the use of comprehensive independent data measurement and processing techniques, as well as their compliance with modern concepts of physics and technology of semiconductors and products based on them. Scientific and practical value of the research results. The scientific value of the research lies in the fact that the study of the mechanisms of mass transfer, diffusion, melting, ablation, defect formation, shockwave processes under the powerful pulsed irradiation of semiconductors and such structures as the film of metal-semiconductor is important for the correct description of ultrafast simultaneously occurring physical nonlinear processes under the powerful nanosecond laser irradiation of crystals. The practical value of the work lies in the fact that in semiconductors CdMeTe the ascertained dominant mechanisms of the mass transfer, calculations of heat and pressure gradients during PLI allow a targeted modification of properties and get new layers and structures with unique optical, photovoltaic properties that will be used in a variety of sensors and detector devices . Implementation of the research results. Based on the results of studying the effect of pulsed laser processing of crystals and nonlinear optical effects on diffusion and defect formation processes: the developed acousto-emission express methods of monitoring and predicting the reliability of semiconductor materials were used in the selection of InGaN LEDs for the serial production of energy-efficient LED luminaires (Reference of Poltava National Technical University, August 15, 2016). Application of the obtained results allowed to increase the light output coefficient of luminaires by 3%; the results obtained for mass transfer mechanisms for nanosecond laser solid-state doping with CdTe by Indium; the mass transfer coefficients of Indium in CdTe; the causes of local melting of compounds of CdTe and GaAs single crystals; established thresholds for the melting of the surface of single crystals with a single nanosecond (20 ns) irradiation with X = 0.694 pm; the established relationship between the processes of acoustic emission generation and changes in luminescent and electrical characteristics of GaN-based heterostructures were used in the implementation of the grant by Karakalpak State University of Berdakh F-2-OT-1-10079 "Peculiarities of laser-induced nonlinear processes of defect formation in semiconductors" 2011-2016 (Reference of the Committee for the Coordination of the Development of Science and Technology of the Republic of Uzbekistan of February 21, 2017). The use of scientific results allowed to develop a nondestructive express method of monitoring and predicting the reliability of LEDs. The results obtained by the mechanisms of the mass transfer of Indium atoms to cadmium telluride and the Raman scattering for Indium and Tellurium materials have been used in foreign journals (Journal of Applied Physics 119, 024106 (2016) 10.1063 / 1.4937996; Chem. Mater., 2014, 26 (7 ), pp 2313-2317, Sensors and Actuators B: Chemical, Volume 191, February 2014, Pages 673-680) to determine the depth of shock wave formation. Approbation of the research results. Results of the research work have been discussed at international 17 and republican 5 scientific and practical conferences. Publication of the results. The main results of the dissertation are published in 17 research papers, 3 papers are in English language, 1 book (monograph), and 9 conference Proceedings. Publication of the research results. 40 scientific works were published on the thesis theme, including 17 articles in journals recommended by the Higher Attestation Commission of the Republic of Uzbekistan for the publication of basic scientific results of doctoral theses. There is 1 utility model patent. The structure and scope of the thesis. The thesis consists of an introduction, five chapters, conclusion and bibliography. Totally there are 208 pages.