Semiconductor crystals
The laboratory "Growth of semiconductor crystals" was created in 1959 under the leadership of academician M.S. Saidov at the Physicotechnical Institute of the Academy of Sciences of the Republic of Uzbekistan. The laboratory conducts research work on the study of physical and chemical technologies for producing semiconductor materials and devices based on them. The main tasks are to establish patterns of interaction and distribution of chemical elements in multicomponent one- and two-phase systems in relation to issues of semiconductor materials and solid-state electronics, especially with solar cells and LEDs.
The main research focus of the laboratory is the elucidation of the physicotechnological features of the synthesis of new solid solutions, models of self-organization in two and multicomponent solid solutions, obtaining nano-, homo- and heterostructures based on elemental semiconductors and semiconductor compounds of class АIIIВV and АIIВVI on silicon substrates, as well as research photovoltaic, thermal voltaic, photothermal and radiative effects in them.
In the laboratory, 5 doctors of science, 5 candidates of sciences, 2 applicants, 2 doctoral candidates, technicians and technicians are engaged in scientific activities.
The main achievements of the laboratory.
New directions of research of semiconductor materials and converters of radiant and thermal energy into electrical energy were founded in the laboratory: 1) continuous solid solutions of semiconductor compounds; 2) impurity photovoltaic.
For the first time, on the basis of an open new phenomenon - the formation of new solid solutions by replacing elementary semiconductors of group IV molecules with molecules of semiconductor compounds from groups III-V and II-VI and a number of theoretical and experimental studies, three concepts have been developed for creating solid solutions and impurity effects in them : 1) On the existence of a new class of semiconductor continuous replacement solid solutions and the prospects for their use; 2) On the ways to implement impurity photovoltaic and photothermoltaic effects in photo and thermal elements in order to significantly improve the efficiency of solar cells and thermo photovoltaic systems; 3) On the physical effects inherent only in solid solutions.
To develop the concept of the existence of a new class of semiconductor replacement solid solutions, the following ideas were put forward: molecular elements C2, Si2, Ge2, Sn2, their combinations CGe, CSn, SiGeSiSn, GeSn and their more complex combinations are new, previously unknown chemical compounds not described by traditional state diagrams, new chemical compounds of elementary semiconductors and binary compounds III-V, II-VI in liquid metallic solvents, at a temperature below the melting point, are in the form of molecules and form t substitutional solid solutions at low temperature crystallization epitaxial layer from the liquid phase. A formula is proposed for the solubility of various elements in multicomponent systems and the conditions for the formation of new substitutional solid solutions are formulated, which consist in the equality of the valence sums and the close values of the sums of the covalent radii of the atoms forming the solution-forming molecules. Under the leadership of Professor A.S. Saidov synthesized on silicon substrates new classes of semiconductor graded-gap continuous solid solutions:
1-class IV1-xIVx: Si1-xGex, Si1-xSnx, Ge1-xSnx;
2-class (IV2)1-x(AIIIBV)x: (Ge2)1-x(GaAs)x, (Si2)1-x(GaP)x, (Ge2)1-x(InP)x, (Sn2)1-x(InSb)x, (Si2)1-x(GaSb)x;
3-class (IV2)1-x(AIIBVI)x: (Ge2)1-x(CdTe)x, (Ge2)1-x(ZnSe)x, (Si2)1-x(ZnS)x, (Si2)1-x(CdS)x, (Si2)1-x(ZnSe)x;
4–class (IV2)1-x-y(AIIIBV)x(AIIBV)y: (Ge2)1-x-y(GaAs)x(ZnSe)y, (Si2)1-x-y(ZnSe)x(GaP)y.
The concept of how to implement impurity photo- and photothermoltaic effects is based on the ideas of the advisability of using isovalent impurity elements and compounds that meet the condition for the formation of solid solutions of molecular substitution based on basic semiconductors. A mechanism for the photovoltaic effect due to isovalent impurities, the energy levels of which are in the valence band, is proposed.
The energy levels of molecules (Si2, Ge2, GaP) of narrow-gap semiconductors located inside the band gap of wide-gap semiconductors of АIIIВV и АIIВVI compounds, as well as the levels of molecules (GaAs, CdS, ZnSe) of wide-gap semiconductors inside the valence band of the narrow-gap semiconductor were detected for the first time.
The two-color radiation of the nGaP-n+(ZnSe)1-x-y(Si2)x(GaP)y diode heterostructure (0 £ x £ 0.03, 0 £ y £ 0.09) due to electronic transitions involving molecular levels of Si2 (red light) and GaP (yellow light) with energy levels of 1.63 eV and 2.2 eV, respectively, located in the forbidden zone of the solid solution (ZnSe)1-x-y(Si2)x(GaP)y.
The thermal effect of silicon obtained by repeated melting of technical silicon in a solar furnace and Si1-xGex variable-gap solid solutions was first discovered, which consists in generating current and voltage when the sample is uniformly heated with ohmic contacts.
For the first time, a photothermal-voltaic effect was discovered in nSi-p(Si2)1-x-y(Ge2)x(GaAs)y, pSi-n+(ZnSe)1-x-y(Si2)x(GaP)y heterostructures, consisting in the generation of current and voltage at a joint photo and heat generation of current carriers under solar cures.
For the first time, on the basis of the developed ideas about the possibility of the development of the processes of self-organization of defects in semiconductors of group III-V, a thermal effect was discovered in these materials.
For the first time, using an environmentally friendly method, polycrystalline silicon with a purity of 99.9 atomic% was obtained in the small solar furnace, eightfold melting of metallurgical silicon with a purity of 96 atomic%, in the open air. The laboratory has prepared 8 doctors of science, including 1 academician of the Academy of Sciences of the Republic of Uzbekistan, 3 laureates of the state prize of the Republic of Uzbekistan, 27 candidates of science.
The laboratory has a complete technological equipment for growing multicomponent solid solutions and homo-and heterostructures based on them, and it is also equipped with the appropriate equipment for analyzing and studying the electrophysical and optical parameters of the structures obtained. This makes it possible to improve the relevant technological processes and improve the characteristics of the structures produced. Studies are conducted using modern scientific equipment with the participation of highly qualified specialists.