Тонкі плівки оксиду диспрозію, утворені при швидкому термічному відпалі на пористих підкладках SiC

In this paper, we consider the effect of rapid thermal annealing (RTA) on the properties of Dy2O3 film formed on the surface of a substrate with a por-SiC/SiC structure. The atomic composition of the films under study was analyzed as a function of the RTA time. It is shown that the RTA method makes it possible to obtain thin Dy oxide films with a composition close to the stoichiometric one. In this case, an increase in the RTA time leads to improving the quality of film-substrate interface and increasing the optical transmission of Dy2O3/por-SiC/SiC structureУ цій роботі розглянуто вплив швидкого термічного відпалу (ШТВ) на властивості плівки Dy2O3, що утворюється на поверхні підкладки зі структурою por-SiC/SiC. Атомний склад досліджуваних плівок аналізували як функцію часу ШТВ. Показано, що метод ШТВ дозволяє отримувати тонкі плівки оксиду диспрозію зі складом, близьким до стехіометричного. У цьому випадку збільшення часу ШТВ призводить до поліпшення якості межі поділу плівка-підкладка і до збільшення оптичного пропускання структури Dy2O3/por-SiC/SiC

Optimization of technological parameters of ohmic contact junctions for GaAs-AlGaAs-based transistor structures

The work deals with study and optimization of the technological parameters of ohmic contacts for HEMTs. It is shown that the depth of fusion front penetration into semiconductor is the main factor that determines ohmic properties of contact junctions

Effect of weak magnetic fields treatment on photoluminescence of III-V single crystals

The long-term transformations of photoluminescence of GaP, GaAs and InP single crystals treated with pulsed weak magnetic fields are obtained. The treatments were performed in two regimes, namely, single-pulse (τ = 30 ms) and multi-pulse (τ = 1.2 ms) ones, at varying magnitudes of magnetic induction. The defect structure transformations were inferred from the radiative recombination spectra in the 0.6-2.5 μm at 77 K. A possible mechanism of observed modifications related to the electron spin transformation is discussed

Influence of pulse magnetic fields treatment on optical properties of GaAs based films

Long-term transformations of the optical reflectance of GaAs epitaxial structure under weak magnetic field treatment (B = 60 mT, f = 10 Hz, τ = 1.2 ms, t = 5 min) have been obtained. Optical measurements were performed within the wavelength range 800…1100 nm at 300 K. Non-monotonous changes of reflectance were observed. Experimental results have been interpreted in terms of diffusion of point defects, resulting from destruction of metastable complexes (probably [VAs+impurity]), from the internal boundaries to the surfaces of the investigated structures. The method for detection of non-equilibrium complexes in multilayer objects has been proposed

Comparison of properties inherent to thin titanium oxide films formed by rapid thermal annealing on SiC and porous SiC substrates

The comparative analysis of optical characteristics inherent to TiO2/SiC and TiO2/por-SiC/SiC structures has been performed. It has been shown that, in these structures regardless of the substrate structure, formation of TiO2 layers with approximately the same width 60 nm takes place. In this case the TiO2 film composition is close to the stoichiometric one. At the same time, the presence of an additional porous layer in the TiO2/por-SiC/SiC structure leads to blurring the oxide film – substrate interface but promotes an increase in the intensity of the Raman scattering signal from the oxide film

Вплив зовнішніх дій на механічні напруження і електронні параметри гетеросистем з С60 фулеренами

The results of a complex study of C60/Si heterosystems are presented in this work: the crystal structure and composition of the films, internal mechanical stresses, electronic parameters of the film and the film-substrate interface, and the effect of external influences (ultraviolet irradiation, thermal annealing, gamma and microwave irradiation). The advantage of microwave treatment over others is established: the absence of fullerene decomposition, the removal of internal mechanical stresses in the heterosystem, and the improvement of its electronic parameters. Methods for remove the decomposition of C60 molecules under the influence of other treatments have been developed. To eliminate the interaction of fullerenes with oxygen, it was proposed to perform thermal annealing and UV irradiation in vacuum, and in the case of g-irradiation, apply a protective coating on the surface of the film (GeOx or SiOx). In solar cells with C6 films in the polymer matrix on Si, a significant advantage of titanium contacts in comparison with gold is established, especially after microwave treatment. Contact resistance decreased as a result of hybridization of 3d-orbitals of titanium and 2p-orbitals of fullerenes with the formation of ТіхС60 carbides and radiation-stimulated diffusion of metals, which increases the contact area.В роботі приведені результати комплексного дослідження гетеросистем С60/Si: кристалічної структури і складу плівок, внутрішніх механічних напружень, електронних параметрів плівки і межі поділу плівка-підкладка та впливу на них зовнішніх дій (ультрафіолетового опромінення, термічного відпалу, гамма та мікрохвильового опромінення). Встановлено перевагу мікрохвильової обробки перед іншими: відсутність розпаду фулеренів, повне усунення внутрішніх механічних напружень в гетеросистемі та покращення її електронних параметрів. Розроблені методи усунення розвалу молекул С60 під дією інших обробок. Термічний відпал і УФ-опромінення пропонується проводити у вакуумі, а для g-опромінення наносити захисне покриття на поверхню плівки (GeOx або SiOx) для усунення взаємодії фулеренів з киснем. В сонячних комірках з плівками С60 в полімерній матриці на Si встановлена суттєва перевага титанових контактів перед золотими, особливо після мікрохвильової обробки. Контактний опір зменшувався в результаті гібридизації 3d-орбіталей титану і 2р-орбіталей фулеренів з утворенням карбідів ТіхС60 та радіаційно-стимульованої дифузії металів, яка збільшує площу контакту

Interface features of SiO₂/SiC heterostructures according to methods for producing the SiO₂ thin films

In this work, we studied comparative characteristics of the SiO₂/SiC heterostructures. The following two techniques were used for SiO₂ formation: thermal oxidation in water vapor (i) and oxidation in solution (ii). According to experimental results obtained from optical absorption and photoluminescence spectra as well as from measurements of internal mechanical stresses, one can conclude that the thin SiO₂ films prepared using the technique (ii) possess SiO₂/SiC interface with a less number of defective states than that for SiO₂ films prepared using the technique (i)

Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts

We investigated temperature dependence of contact resistance of an Au−Ti−Pd₂Si ohmic contact to heavily doped n⁺ -Si. The contact resistance increases with temperature owing to conduction through the metal shunts. In this case, the limiting process is diffusion input of electrons to the metal shunts. The proposed mechanism of contact resistance formation seems to realize also in the case of wide-gap semiconductors with high concentration of surface states and dislocation density in the contact

Properties of SiO₂-GaAs and Au-Ti-SiO₂-GaAs structures used in production of transmission lines

We investigated electrophysical properties of the SiO₂-GaAs and Au-Ti-SiO₂-GaAs structures that are used in technological process when manufacturing transmission lines for microwave integrated circuits. The SiO₂-GaAs structures were formed using different techniques, namely, (i) monosilane oxidation in oxygen, (ii) high-temperature tetraethoxysilane decomposition, (iii) high-frequency cathode sputtering of quartz in argon plasma, and (iv) electron-beam evaporation of quartz in a vacuum. The SiO₂ films obtained using monosilane oxidation or electron-beam evaporation of quartz demonstrated better properties. For the Au-Ti-SiO₂-GaAs structures a layer structure transformation was shown to occur, with formation of TiOx-SiO₂ junction and gold atoms penetration over the whole adhesion layer thickness. The microwave oscillator modules made using the Au-Ti-SiO₂-GaAs (Si) structures demonstrated output power of 10-60 mW in the 8 mm wavelength range

Technique and setup for diagnostics of p-n junction to case thermal resistance in high-power gallium nitride LEDs

We present a setup and procedure of studying p-n junction to case thermal resistance in high-power light-emitting diodes (LEDs) from their thermal relaxation. A set of LEDs mounted on a metal-core printed circuit board (MCPCB) were studied. The contributions to the total thermal resistance from a heavy heat sink, MCPCB, heat slug and LED chip are separated