Features for the Design of A Specialized Information-measuring System for the Study of Thermoelectric Properties of Semiconductors

Methods for studying thermoelectric parameters of semiconductors that are optimal for the implementation of software and hardware have been analyzed and selected. It is based on the Harman method and its modifications, adapted for pulse measurements, which are convenient to implement on a modern element base. An important advantage of these methods is the absence of the need for accurate measurements of heat fluxes, which greatly simplifies and reduces the time for conducting experimental research. The required operating ranges for the voltage 10 µV–1 V, for the current 10 µA–300 mA and the element base performance at the processing level of 40–200 million samples per second have been determined. Structural and electrical circuits, as well as software for a specialized computer system for studying thermoelectric parameters of both bulk and thin-film thermoelectric materials, and express analysis of the operational characteristics of finished modules have been developed. It has been shown that the proposed scheme copes well with the task. And the use of FPGA and 32-bit microcontrollers provide sufficient processing speed up to 200 MSPS and the necessary synchronization modes for the implementation of the Harman pulse method even when studying films of nanometer thickness. Experimental studies of both bulk thermoelectric modules based on Bi2Te3 and thin-film thermoelectric material based on PbTe have been carried out. The effectiveness of the developed tools and techniques has been shown, which made it possible to more than halve the time for sample preparation and experiment. Based on the presented models, all the main thermoelectric and operational parameters have been determined, in particular, electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric figure of merit. As a result of the development of specialized computer tools, it was possible to reduce the labor intensity of the process of measuring the main electrical and operational parameters of semiconductor thermoelectric materials and energy conversion modules based on them, as well as to automate the process of defects identification of thermoelectric modules. The labor intensity of the research process has decreased not only due to the automation of the measurement process, but also due to an optimized technique that allows research on a sample of one configuration, since the manufacture and preparation of samples are the most laboriou

Development of Technology of Superconducting Multilevel Wiring in Speed GaAs Structures of LSI/VLSI

Technological aspects of the use of superconducting materials are considered and the possibility of making targets for magnetron deposition of films for the formation of cryoconductive wiring in GaAs-based LSI-structures is shown. The technological methods and regimes are determined and high-performance technology of cryoalloys making based on Al, Nb, V with Si, Ge and rare-earth metal admixtures and magnetron formation of superconducting films from aluminum, niobium and vanadium alloys are developed. In particular, technological regimes (ion current, accelerating voltage, deposition rate, plasma composition, uniformity of components per silicon substrate diameter) have been established, which provide a thickness of films at the level of 0.6-1 μm. Insignificant thermomechanical stresses (about 1 kg/cm2) and small grain size (~ 10 nm) will allow for excellent adhesion of deposited films and formation of a topological pattern of submicron sizes using photolithography.The parameters and characteristics of the Schottky field GaAs transistors on homo- and heterostructures (Schottky barrier height 0.75-0.8 eV, non-ideality factor 1.2-2, breakdown voltage of Schottky barrier 15-30 V) are explored and methods for increasing the speed of the LSI-structures are defined. It is shown that increasing the speed of LSI/VLSI-structures on gallium arsenide is achieved by using thermostable cryomaterials as gate electrodes, conductors and contacts of source-drain regions of the Schottky field-effect transistors

Research Into Constructive and Technological Features of Epitaxial Gallium-arsenide Structures Formation on Silicon Substrates

The technology of formation of LSI structures on GaAs epitaxial layers, formed on Si-substrates of large diameter, is developed, which makes it possible at least by an order of magnitude to reduce the production cost of crystals due to epitaxial growth of GaAs layers and the use of technological equipment of silicon technology. This technology also enables the useof heterostructures to increase the speed of the LSI.An analysis of complex structures of different architecture of IC/LSI on GaAs epitaxial layers, formed on Si-substrates, is carried out. The influence of the scattering processes of charge carriers on the potential fluctuations on the magnitude and profile of the mobility of electrons along the thickness of the epitaxial structure is investigated. When using epitaxial technology in structures, there are no isoconcentric impurities of oxygen and carbon, which are the factors of scattering of charge carriers, which makes it possible to achieve high values of mobility of charge carriers.It is shown that the use of epitaxial layers of gallium arsenide eliminates the effects of isoconcentration impurities of oxygen and carbon in gallium arsenide layers that increases their purity.A test element was implemented that allows non-destructive measurement of the mobility of charge carriers in the technological cycle of the formation of LSI structures. This allows us to realise the electrophysical diagnosis of the reliability of the LSI at the stage of crystal manufacturin

Methods of Computer Tools Development for Measuring and Analysis of Electrical Properties of Semiconductor Films

The method is presented and computer tools of automated measurement of electrical parameters and experimental data processing are developed, taking into account models for describing physical processes that determine the operating characteristics of semiconductor material. The possibility of automated investigation of the quality and ohmicity of contacts is realized, which significantly improves the reliability of the data obtained.Methods and features of software processing of automated research results are considered using the models that allow taking into account the effect of surface, structure and thickness of the sample on the electrical properties of semiconductor films.Experimental studies of a series of n-PbTe thin films are carried out and the efficiency of the developed tools and methods of processing scientific data using the described methods of experimental data analysis is shown. Based on the simulation, the electrical parameters of the surface layers were determined and the effect of the surface and grain boundary mechanisms of charge carrier scattering on the electrical parameters of the films was separated. The surface mobility of the charge carriers is approximately 3 times less than the mobility in the bulk material, which indicates the dominance of the diffuse scattering of charge carriers on the surface of the thin-film samples despite the high reflectance coefficient (0.4). Taking into account the effect of the surface and the boundaries of the grains, it is possible to choose the technological modes and duration of spraying to obtain a semiconductor material with the desired properties.As a result of using the developed tools, it was possible to significantly reduce the complexity of the process of measuring the basic electrical parameters of semiconductor materials, processing the experimental results, to improve the accuracy of the results obtaine

Features of Formation of Microwave GaAs Structures on Homo and Hetero-transitions for the Sub-microconnection of the Lsic Structures

The features of the formation of microwave GaAs structures are considered and a set of studies is carried out to create a serial technology of large-scale integrated circuit structures (LSIC), including the number of microwaves on GaAs epitaxial layers deposited on monosilicon substrates.The conditions for the formation of a two-dimensional electron gas in hetero-structures with the determination of electron mobility depending on the orientation of the surface were investigated. For hetero-structures on the surface of a semi-insulated GaAs substrate rotated from the plane (100) at an angle of 6–10º with oxygen content on the initial surface С0=10–50 % relative to the gallium peak of the Auger spectrum, a strong mobility anisotropy was found due to an increase in the angle of reorientation and incomplete annealing of carbon from the initial surface of the GaAs substrate.For the deposited layers of gallium arsenide on monosilicon substrates epitaxial technology is used, which can significantly improve the purity of the obtained material, namely, significantly reduce the level of oxygen and carbon isoconcentration impurities, which strongly affect the charge state of the interface.For the formation of structural layers on GaAs, the technology for the formation of nitride layers of Si3N4, AlN, BN by the magnetron method at low substrate temperatures and a given stoichiometry was developed and investigated. The combination of gallium epitaxial nano-silicon arsenide technology to silicon substrates became realistically possible only with the development of technology of magnetron precipitated buffer layers of germanium.The technology of the formation of logical elements NOT, OR-NOT, AND-NOT of high speed with low threshold voltage is developed, which allows to build high-speed chips of combination and sequential types on complementary structure