Raisa Konakova

National Academy of Sciences of Ukraine | ISP · V. E. Lashkaryov Institute of Semiconductor Physics

In this work, the authors have considered the effect of short-term nonthermal action of microwave radiation on the distribution of radiative recombination centers in SiC/por-SiC/Dy2O3 structures. The analysis of photoluminescence spectra of these structures excited by the radiation with an energy lower than the band gap in the 4H-SiC crystalline su...

The relationship between internal mechanical stresses, surface morphology, nanoscale electrical properties, and optical characteristics in TiO2, Gd2O3, Er2O3, and SiO2 thin films on SiC substrates was investigated. The oxide films were synthesized using the rapid thermal annealing and analyzed through scanning spreading resistance microscopy, photo...

In this work, the authors have considered the effect of short-term nonthermal action of microwave radiation on the photoluminescent characteristics of SiC/por-SiC/Er2O3 and SiC/por-SiC structures. The analysis of photoluminescence spectra of these structures, which are excited by radiation with an energy lower than the band gap in the 4H-SiC crysta...

In this work, comparative characteristics of thin oxide films (OF) of titanium, erbium, and dysprosium formed on silicon carbide substrates in the presence and absence of a porous silicon carbide (por-SiC) layer have been considered. It has been shown that regardless of the presence of a porous buffer layer in the TiO2(Er2O3, Dy2O3)/por-SiC/SiC and...

The method of processing the data of electrophysical investigations of ohmic contacts has been developed. It allows obtaining more accurate results of measuring the contact resistance and additional information by analyzing the statistical and spatial distribution of input data. To test the method, the Au–Ge–TiB2–Au contact to n-n+-GaAs was used. T...

The temperature dependences of the specific contact resistance of silicon roc with a doping step are measured experimentally and described theoretically. The measurements are performed in the temperature range from 4.2 to 380 K. It is established that the contacts of the studied Au–Ti–Pd–n+–n-Si structures are ohmic. It is shown that minimal roc is...

Wepresent a study of the modifications to the optical transmittance of GaN thin film on sapphire due to weak magnetic field (WMF) treatment. Measurements were performed in the 320-1100 nm wavelength range at 300 K, evidencing a change in transmission spectra for wavelengths above 700-800 nmafter theWMFtreatment.Weuse a model with three layers to si...

This review is devoted to presentation and analysis of physical mechanisms of ohmic contacts formation in semiconductors. In addition to the classical mechanisms known for decades, new mechanisms for current flow in ohmic contacts researched for the recent decade are described. Used in this review were the original results of the authors, which the...

Analysis of the contact-barrier height taking into account the distribution of surface states along coordinate x perpendicular to the insulator–semiconductor interface is performed for metal–semiconductor contacts with a dielectric gap. It is shown that taking into account the spatial dependence of the density of surface states at rather high semic...

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)....

Electrical properties of low-threshold field emission cathodes produced by growth nanocluster graphene films on the pointed surface of heavily doped n⁺SiC by sublimation epitaxy have been considered. The quality of the graphene coating has been assessed based on the morphological studies and Raman spectroscopy. Using the volt–ampere characteristics...

Resistivity ρc of InP- and GaAs-based ohmic contacts has been measured in a temperature range of 4.2–300 K. Both temperature dependences are nonmonotonic and exhibit minima at T = 50 K for InP and T = 150 K for GaAs. The nonmonotonic ρc(T) curves for GaAs contacts have been observed for the first time. The obtained experimental temperature dependen...

Effect of microwave radiation (24 GHz) on transformation of impurity-defect complexes in CdTe:Cl single crystals within the spectral range 1.3…1.5 eV was studied using the low-temperature (T = 2 K) photoluminescence (PL) technique. The shapes of donor-acceptor pairs (DAP) and Y PL bands were studied in detail. The Huang-Rhys factor was calculated f...

Спосіб зниження внутрішніх механічних напружень в епітаксійній структурі GaN/Аl 2 О 3 здійснюють зовнішньою обробкою. Контрольовані структури піддають впливу імпульсного магнітного поля з індукцією 60-70 мТл, тривалістю імпульсу 1,0-4,0 мс, частотою слідування імпульсів 5-15 Гц і тривалістю дії на структури 7-9 хв.

Presented in this paper are experimental data on structural properties of contact metallization and temperature dependence of the specific contact resistance for ohmic contacts Au–Ti–Pd–n+-InP and Au–Ti–Ge–Pd-n+-InP prepared using the method of successive thermal evaporation of metals in oil-free vacuum in one process cycle onto the n+-n-n++-n+++-I...

The structural properties of high-doped n-InN heteroepitaxial films and Au-Ti-Pd-InN ohmic contacts were analysed. The mosaic structure of the InN films was shown by X-ray diffraction. The level of screw dislocations exceed 108 cm-2 , the level of edge dislocations exceed 109 cm-2 . It was found, that enrichment of InN films by indium leads to the...

The properties of a point field-emission cathode representing a structure in the form of a silicon carbide tip coated with a thin graphene film are assessed. For the point cathode with the graphene coating, the current–voltage characteristics are constructed in the Fowler–Nordheim coordinates; the work functions φ of the point cathode are calculate...

The effect of microwave radiation on the luminescence properties of CdS and CdTe:Cl single crystals is studied. It is established that the exposure of these semiconductors to short-term (≤30 s) microwave radiation substantially modifies their impurity and defect structure. The mechanisms of transformation of the defect subsystem of II–VI single cry...

Оптичний спосіб оцінки коефіцієнтів дифузії метастабільних точкових дефектів в епітаксійних структурах на основі GaN базується на вимірюванні оптичних спектрів. Вимірюють спектри оптичного пропускання в інтервалі довжин хвиль 330-1100 нм і додатково вимірюють спектри фотолюмінесценції в інтервалі 350-600 нм. Після цього контрольовані структури п...

Using optical absorption and Auger spectrometry techniques, we studied the effect of rapid thermal annealing (RTA) on the properties of erbium oxide films deposited onto a porous silicon carbide buffer layer formed on 4H-SiC substrates. An analysis of atomic composition of the films under investigation as a function of RTA duration was performed. I...

The temperature dependences of the contact resistivity (ρc) of ohmic contacts based on the Au–Ti–Pd–InN system are measured at an InN doping level of 2 × 1018 cm–3 in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρc(T) are obtained. The dependences are explained within the mechanism of thermionic cur...

An analysis is made of the conditions for ohmic contacts realization in the case of Schottky contacts. Based on the classical notions about the mechanisms of current flow, we consider the generalized model of Schottky contact that takes into account the thermionic current of majority charge carriers and recombination current of minority charge carr...

The temperature dependences of the contact resistivity (ρc ) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 1018 cm−3 in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρc (T) are obtained. The dependences are explained within the mechanism of thermionic c...

The temperature dependences of the contact resistivity (ρ c ) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 1018 cm−3 in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρ c (T) are obtained. The dependences are explained within the mechanism of thermionic...

Experimental data on manufacturing the ohmic contacts Au–Ti–Pd–n+-InP, formed using vacuum deposition of metal onto a heated to 300 °C substrate representing an epitaxial n+-n-n++-n+++-InP structure. The specific contact resistance measured at room temperature was about 7∙10–5 Ohm∙cm2. Voltage-current characteristics within the temperature range 11...

The results of optical studies of the effect of pulsed magnetic field (B = 60 mT, τ = 1.2 ms, t = 5 min) on the structural perfection and recombination properties of epitaxial GaN films grown on sapphire are presented. Nonmonotonic changes in the spectral dependence of transmittance and photoluminescence were detected for GaN films after exposure t...

The effect of microwave irradiation (f = 2.45 GHz, 1.5 W/cm2, t = 1 or 2 min) on the reflectance and photoluminescence spectra of the epitaxial n-n +-GaAs and Au-n-n +-GaAs structures is studied. Short-term microwave irradiation is shown to cause long-term nonmonotonic changes in the spectral characteristics, which can result from the structure mod...

The temperature dependence of the contact resistivity ρc (T) of Au-Ti-Al-Ti-n +-GaN ohmic contacts is studied experimentally and substantiated theoretically in the temperature range T = 4.2–300 K. It is shown that the saturation portion of ρc (T) is observed in the low-temperature measurement region (4.2–50 K). As the temperature increases, ρc decr...

Long-term transformation of the optical transmittance and integral photoluminescence (PL) of GaN epitaxial structure under weak magnetic fields treatment (B¼60 mT, τ¼1.2 ms, t¼5 min) were obtained. Optical and PL measurements were performed at 300 K in the wavelength ranges of 350–1100 nm and 350–650 nm, respectively. Non-monotonic changes of lumin...

The results of the atomic-force microscopy, optical-absorption spectroscopy, and photoluminescence spectroscopy of porous silicon carbide (por-SiC) produced by anodic etching are reported. Analysis of the data shows that the cubic SiC phase is lacking in the porous layer and the photoluminescence signal from por-SiC at the excitation photon energy...

The effect of laser radiation on the characteristics of amorphous silicon films on glassy or quartz substrates are studied by Raman spectroscopy. It is established that an increase in the laser-treatment power yields a phase transition from amorphous silicon to nanocrystalline silicon. The variation in the relation between the nanocrystalline and a...

It is experimentally found that an ohmic contact based on Au-Pt-Ti-Pd-n +-Si metallization is formed due to nanoscale metal shunts containing Si, Au, and Pt in the region of the interface with n +-Si, which appears during heat treatment at T = 450°C for 10 min in a vacuum chamber with a residual pressure of 10−6 Torr. The high density of shunts adj...

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 inferr...

The influence of a microwave treatment (MWT) on the optical properties of hexagonal GaN films has been studied. To estimate the internal mechanical strains and the degree of structural perfection in a thin near-surface layer of the film, the electroreflectance (ER) method is used. The ER spectra are measured in the interval of the first direct inte...

Contact resistivity rc of InP and GaAs based ohmic contacts was measured in the 4.2/300 K temperature range. Nonmonotonic dependences rc(T), with a minimum at temperature 50 K (150 K) for InP (GaAs) based contacts were obtained. The results can be explained within the framework of the mechanism of current flow through metal shunts (associated with...

We present the results of structural and morphological investigations of interactions between phases in the layers of Au-Pd-Ti-Pd-n+-GaN contact metallization that appear at rapid thermal annealing (RTA). It is shown that formation of ohmic contact occurs in the course of RTA at Т= 900C due to formation of titanium nitride. We studied experimental...

The temperature dependences of the contact resistance ρc (T) of ohmic Pd-Ti-Pd-Au contacts to n-GaN and n-AlN wide-gap semiconductors with a high dislocation density are studied. The dependences ρc (T) for both contacts contain portions of exponential decrease ρc (T) and very weak dependence ρc (T) at higher temperatures. Furthermore, a plateau por...

The raman scattering (RS) spectra of graphene on semi-insulating and conductive 6H-SiC substrates formed by preliminary and additional annealing of silicon carbide at various temperatures are studied. The degree of perfection of the graphene films and sizes of its clusters are estimated. It is shown that the temperature of additional annealing in t...

Anomalous temperature dependences of the specific contact resistance ρc (T) of Pd2Si–Ti–Au ohmic contacts to lapped n�Si with dopant concentrations of 5 ×1016, 3 ×1017, and 8 ×1017cm–3 have been obtained. The anomalous dependences of ρc (T) have been accounted for underthe assumption that the current flows along nano-dimensional metallic shunts, wh...

We studied Au-Pd-Ti-Pd ohmic contacts made by thermal evaporation of metals in vacuum onto n-GaN (n-AlN) with high dislocation density heated to a temperature of 350 °�. Temperature dependence of ohmic contacts resistivity may be described by the mechanism of current flow through the metal shunts associated with dislocations, with allowance made fo...

We studied Au-Pd-Ti-Pd ohmic contacts made by thermal evaporation of metals in vacuum onto n -GaN (n -AlN) with high dislocation density heated to a temperature of 350 °C. Temperature dependence of ohmic contacts resistivity may be described by the mechanism of current flow through the metal shunts associated with dislocations, with allowance made...

We present experimental results concerning a high density of structural defects (in particular, dislocations) in the near-contact region of heavily doped n-silicon. They appear in the course of firing Au Pd Ti Pd –Si -n ohmic contact at 450 С for 10 min in a vacuum of ~10 Pa-4. These defects lead to appearance of metal shunts that determine the cur...

Measuring data for the parameters of a microstrip switching superhigh-frequency integrated circuit on a 100 μm thick polycrystalline diamond film are reported. Measurements are taken in the frequency range 3–7 GHz. It is shown that the decay in developmental modulators is no greater than 1.5 dB in the on state and no less than 29 dB in the off stat...

We studied, both theoretically and experimentally, temperature dependences of contact resistivity, ρc(T), of ohmic contacts to n+-GaN. The ρc(T) curves have saturation portion at low temperatures (4.2-50 K) and exponential portion as temperature grows up to 300 K. For comparison we also give the reference data on ρc(T) for ohmic contacts to n+-GaAs...

We studied ohmic contacts Au-Pd-Ti-Pd-n-AlN and Au-TiB2-Al-Ti-n-GaN with contact resistivity $rho$с = 0.18 Ohm*cm^2 and 1.6*10^-4Ohm*cm^2, respectively, and the effect of microwave treatment on their electrophysical properties. After microwave treatment for time t up to 1000 s, the contact resistivity dropped by 16% (60%) in the contact to AlN (GaN...

We studied temperature dependences of resistivity, , of Pd-Ti-Pd-Au ohmic contacts to wide-gap semiconductors n-GaN and n-AlN with high dislocation density. Both curves have portions of exponential decrease, as well as those with very slight dependence at higher temperatures. Besides, the Au-Pd-Ti-Pd-n-GaN contacts have a portion of flattening out...

The nanomechanical properties of pure and doped Ta2O5 films (100 nm) on Si, and the effect of short time (10 s) microwave irradiation are studied by nanoindentation testing. The local mechanical parameters as determined by the force measuring ability of atomic force microscopy are compared with the data from both the Oliver–Pharr nanoindentation te...

The surface morphology and the Raman and photoluminescence spectra of a SiC/por-SiC/TiO2 structure before and after rapid thermal annealing are studied. It is shown that rapid thermal annealing brings about the appearance of new bands in the Raman spectrum; these bands are characteristic of carbon compounds. An analysis of the spectra of photolumin...

Transistor heterostructures with high-carrier-mobility have been studied. It is shown that, as the γ-irradiation dose Φ increases, their degradation occurs in the following sequence. (i) At Φ < 107 rad, the GaAs surface layer is damaged to a depth of 10 nm due to a >0.2-eV decrease in the diffusion energy of intrinsic defects and, probably, atmosph...

The temperature dependence of contact resistivity qc in lapped silicon specimens with donor concentrations of 5*1016, 3*1017, and 8*1017 cm-3 was studied experimentally. We found that, after decreasing part of the qc(T) curve in the low temperature range, an increasing part is registered with increasing temperature T. It is demonstrated that the fo...

A new mechanism of contact resistance formation in ohmic contacts with high dislocation density is proposed. Its specific feature is the appearance of a characteristic region where the contact resistance increases with temperature. According to the mechanism revealed, the current flowing through the metal shunts associated with dislocations is dete...

Temperature dependences of the contact resistivity ρc of Au-TiBx -Ge-Au-n-n +-n ++(GaAs)-InP ohmic contacts before and after short-term (10 s) microwave treatment have been studied both experimentally and theoretically. It is shown that ρc can decrease after microwave treatment in the entire temperature range of ρc measurements (100–400 K). Good ag...

Based on a theoretical analysis of the temperature dependence of the contact resistance R c for an Au-Ti-Pd2Si-n +-Si ohmic contact, a current-transfer mechanism explaining the experimentally observed increase in R c in the temperature range 100–380 K is proposed. It is shown that microwave treatment of such contacts results in a decrease in the sp...

Experimental data on the electroreflectance spectra of {gamma}-irradiated epitaxial GaN films on sapphire are reported. The irradiation doses are 10{sup 5}-2 Multiplication-Sign 10{sup 6} rad. The theoretical electroreflectance spectra calculated on the basis of a model of three types of transitions are in agreement with experimental data with reas...

A new mechanism describing the rise in the contact resistance ρc of ohmic contacts to n-n +-n ++-GaAs(GaP, GaN, InP) structures with increasing measurement temperature T, experimentally observed in the temperature range 100–400 K, is suggested on the basis of a theoretical analysis of the temperature dependence of ρc . Good agreement between the ex...

We studied temperature dependences of resistivity ρc(T) of Pd-Ti-Pd-Au ohmic contacts to wide-gap semiconductors n-GaN and n-AlN with high dislocation density. The obtained dependences cannot be explained by the existing mechanisms of current flow. We propose possible mechanisms explaining the experimental ρc(T) curves for ohmic contacts to n-GaN a...

Endothermic reactions were observed as a result of low-power microwave radiation. Composite microhardness changed because of structure relaxation of intergranular ordering.

Спосіб відбраковування потенційно ненадій- них гомоепітаксійних структур на основі GaAs та ІnР, що базується на вимірюванні спектрів оптич- ного відбиття в інтервалі довжин хвиль 900-1200 нм, який відрізняється тим, що контрольовані структури після вимірювання спектра оптичного відбиття додатково піддають впливу імпульсного магнітного поля з і...

Some aspects of measuring the thermal resistance to a constant heat flow at a p-n junction–package region in IMPATT and light-emitting diodes are considered. We propose a method of studying the thermal resistance of high-power light-emitting diodes. This method makes it possible to increase accuracy of measuring the thermal resistance by determinin...

Монография охватывает базовые физические методы диагностики в микроэлектронике: методы рентгеновской дифракционной диагностики полупроводниковых материалов и структур для СБИС и ряда дискретных полупроводниковых приборов, а также полупроводниковых структур с квантовыми точками, квантовыми ямами и сверхрешетками; методы электронной микроскопии, Оже-...

The effect of microwave radiation on the transformation of impurity-based structural complexes in CdTe:Cl single crystals is studied using low-temperature photoluminescence measurements. It is shown that microwave radiation activates ClTe centers, resulting in an increase in the intensity of photoluminescence line of excitons bound at the correspon...

The methods of high-resolution X-ray diffraction have been used to study the multilayered structures in an In x Ga1 − x N/GaN system grown by the method of metal-organic chemical-vapor deposition. A correlation between the strain state (relaxation) of the system, the indium content within quantum wells, the ratio of the barrier/well thicknesses, an...

The methods of high-resolution X-ray diffraction have been used to study the multilayered structures in an InxGa1–xN/GaN system grown by the method of metal–organic chemical-vapor deposition. A correlation between the strain state (relaxation) of the system, the indium content within quantum wells, the ratio of the barrier/well thicknesses, and the...

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 form...

The thermal limits of the two-drift impact avalanche and transit-time (IMPATT) diode operating in the pulsed mode in the 8-mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p-n junction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C...

High resolution X-ray diffractometry (HRXRD) was used to investigate InxGa1−xN/GaN multilayered structures grown by the metal-organic chemical vapor deposition (MOCVD) method. Deformation conditions in the superlattice (SL) and its separate layers, degree of relaxation in the structure layers, as well as the period of the SL, thicknesses of its lay...

The thermal limits of the two�drift impact avalanche and transit�time (IMPATT) diode operating in the pulsed mode in the 8�mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p–njunction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C r...