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Background. Malignant melanoma is steadily exaggerating over the recent decades. Nonetheless, improved systemic therapies have substantially increased life expectancy in patients with a locally advanced or disseminated disease. Higherincidence recurrent melanocytic skin lesions become essentially problematic and require more attention and control.Aim. Cross-survey on the incidence of synchronous multiple primary melanomas in patients with solitary melanoma and those with other operable solid tumours.Materials and methods. A total of 289 patients with suspected malignant pigmented skin melanoma were included in the survey. Patients were divided in two cohorts by the presence of primary skin melanoma and its tractability for radical excision. Patients with operable melanoma comprised the study cohort, and those with other solid tumours were the control.Results and discussion. The survey covered 289 patients, with 148 in the study and 141 in the control cohort. The study148 patients revealed 112 malignant pigmented melanomas, but none in the control cohort. A chi-square statistical analysis of clinical values in single and multiple melanoma cases showed a slightly higher prevalence of first-visit melanomas in patients with synchronous tumours (30% pT4 — p = 0.007).Conclusion. The observed 10% rate of second melanoma in the study cohort and a zero melanoma incidence in the control support the alternative hypothesis of a higher rate of newly detected melanomas in primarily diagnosed melanoma patients vs. those with solid tumours.

The C–V characteristics of Au/Al2O3/In0.52Al0.48As and Au/SiO2/In0.52Al0.48As metal–insulator–semiconductor structures have been studied. It has been established that the fragmentary measurement of the C–V characteristics of InAlAs-based metal–insulator–semiconductor structures, in contrast standard registration method to at a constant voltage sweep rate, significantly weakens the effect of the hysteresis phenomena and allows one to record stationary curves. It is shown that the density of fast interface states calculated by the Terman method from such C–V characteristics slightly changes over the InAlAs band gap and amounts to (3–6) × 1011 and (1–3) × 1011 eV–1 cm–2 for MIS structures with Al2O3 and SiO2, respectively.

Growth-related structural defects present on the surface of InAlAs layers grown by molecular beam epitaxy on InP(001) substrates influence the temperature dependences of the current–voltage characteristics of Au/Ti/InAlAs Schottky barriers. It is established that these defects in the form of pits cause the appearance of regions with reduced barrier height. At a surface density of ≥107 cm–2, these defects significantly influence the parameters of the Schottky barriers at temperatures below 200 K.

Design and manufacturing technology of high-power microwave Schottky photodiodes with microstripe leads have been developed based on an InAlAs/InGaAs heterostructure. The operating frequency of photodiodes with a mesa diameter of 15 μm is above 25 GHz and a maximum output microwave power at 20 GHz exceeds 50 mW, which allows these photodiodes to be employed in analog fiber-optic microwave signal transmission lines, as well as for the microwave signal generation and processing by optical methods in remote sensing and measuring microwave technology.

The morphology, chemical composition, and electronic properties of Al2O3/InGaAs interfaces with and without anodic oxide layers, formed in DC plasma (O2, Ar) with different contents of the fluorinating component (CF4), were studied. It is shown that thin fluorinated anodic oxide layers, in combination with annealing at 300 °C, reduce the density of interface states by a factor of 3–4 over the entire bandgap. The minimum state density values near the midgap determined by the Terman method are about 2 × 1012 eV−1 cm−2. However, it is demonstrated that, in contrast to the Al2O3/InGaAs interface, the interface with a fluorinated oxide is not stable and degrades when heated above 300 °C.

The design, manufacturing and DC and microwave characterization of high-power Schottky barrier InAlAs/InGaAs back-illuminated mesa structure photodiodes are presented. The photodiodes with 10 and 15 μm mesa diameters operate at ≥40 and 28 GHz, respectively, have the output RF power as high as 58 mW at a frequency of 20 GHz, the DC responsivity of up to 1.08 A/W depending on the absorbing layer thickness, and a photodiode dark current as low as 0.04 nA. We show that these photodiodes provide an advantage in the amplitude-to-phase conversion factor which makes them suitable for use in high-speed analog transmission lines with stringent requirements for phase noise.

The InAlAs surface morphology (AFM), chemical composition (XPS) and the Ti/InAlAs interface structure (HREM), during the Au/Ti/n-In0.52Al0.48As/InP(001) mesa-structure Schottky barrier formation, were studied. The current-voltage (I-V) dependences analysis of the formed Schottky barrier in the temperature range of 100–380 K was carried out. It was shown that the I-V dependences are well described by the thermionic emission theory at temperatures above 200 K with the ideality factor and the barrier height close to 1.09 and 0.7 eV, respectively. At temperatures below 200 K, the I-V behavior is attributed to the Schottky barrier anomalies, which are explained by the existence of nanometer-sized patches with a low barrier height having a Gaussian distribution (Tung model). According to this model, the temperature dependences of the barrier height and ideality factor were described with the following parameters: the homogeneous barrier height of 0.88 eV and standard deviation of 10−4 cm2/3V1/3. In the analysis of the modified Richardson plot, the Richardson constant (10.7 Acm−2 K−2) and the area fraction (24%), occupied by the patches with a low barrier height and diameter ~80 nm, were calculated. The patches appearance is explained by the presence of the spikes detected on the InAlAs surface by the AFM method.

The comparative experimental and theoretical studies of the fluorine/oxygen ratio influence on the structural and electronic properties of anodic layer (AL)/InAs interface by XPS, HRTEM, C-V measurements and ab initio calculation of fluorine and oxygen adsorption on the InAs(111)A-(1×1) unreconstructed surface were performed. The well-ordered transition region (TR), composed of indium and arsenic oxyfluorides, and extension of the interplanar distance at the fluorinated anodic layer (FAL)/InAs interface were experimentally revealed. The theoretical modeling of AL/InAs and FAL/InAs interfaces showed that the fluorinated TR formation removes the InAs surface distortion, whereas the In(InAs)-F-As(FAL) and In(InAs)-O-As(FAL) bonds formation is a reason for the interplanar distance increase between FAL and the InAs surface. The decrease of the interface states density in the InAs bandgap and the Fermi level unpinning at the FAL/InAs interface result from the positive charge increase on FAL arsenic atoms near t...

The influence of InAlAs/InP(001) heterostructures surface morphology on the optical properties (dispersive refractive index and extinction coefficient) of the anodic layer, formed by the oxidation in low-energy Townsend gas-discharge O2-Ar-containing plasma at room temperature, was studied using atomic force microscopy and ellipsometry methods. High resolution transmission electron microscopy and X-ray photoelectron spectroscopy were used to determine the anodic layer morphology and chemical composition. It is shown that the growth structural defects (pits) on the InAlAs surface, with a density 106–107 cm−2, do not significantly influence the optical properties of the amorphous anodic layers, mainly consisting of In2O3, Al2O3, As2O3 and elemental arsenic quite uniformly distributed over their depth and area. The thickness of thin (≤10 nm) oxide layers on InAlAs is measured at a high accuracy by the nondestructive ellipsometry method using the optical model of a single-layer isotropic film on an absorbing substrate.

Current–voltage (I–V) characteristics of Au/Ti/n-InAlAs/InP Shottky barriers have been studied in a temperature range of 100–380 K. It is established that, as the temperature increases from 100 to 200 K, the ideality factor drops from 1.58 to 1.1, while the barrier height grows from 0.55 to 0.69 eV. With a subsequent temperature increase from 200 to 380 K, both the ideality factor and barrier height vary, but only weakly. This behavior agrees well with the model of lateral inhomogeneity of the barrier height (Tung model), which is confirmed by the linear dependence of the barrier height on the ideality factor at temperatures within 100–200 K. Calculations according to this model yielded the value of 0.88 eV for the homogeneous-junction barrier height, 10–4 cm2/3 V1/3 for the mean-square deviation of the Gaussian distribution of barrier heights, 3.7 × 10–11 cm2 for the effective area of regions with reduced barrier heights, and 10.7 A cm–2 K–2 for the Richardson constant.

The projector augmented-wave method is applied for investigation of oxygen and fluorine adsorption on the cation-terminated InAlAs(111) unreconstructed surface. The binding energies of both adsorbates with semiconductor surface are estimated. Their influence on the surface band structure and states within band gap is analyzed. It is shown that oxygen adsorption leads to appearance of additional surface states in the fundamental gap, whereas fluorine coadsorption results in partial or complete removal of the surface state and an unpinning of the Fermi level.The projector augmented-wave method is applied for investigation of oxygen and fluorine adsorption on the cation-terminated InAlAs(111) unreconstructed surface. The binding energies of both adsorbates with semiconductor surface are estimated. Their influence on the surface band structure and states within band gap is analyzed. It is shown that oxygen adsorption leads to appearance of additional surface states in the fundamental gap, whereas fluorine coadsorption results in partial or complete removal of the surface state and an unpinning of the Fermi level.

In the paper, high-power InGaAs/InAlAs Schottky photodiode with low amplitude-to-phase noise conversion is presented. It is shown that photodiode cutoff frequency is 28 GHz and maximal output microwave power is 58 mW at the frequency of 20 GHz. Amplitude-to-phase noise conversion coefficient of the proposed photodiode is demonstrated to be less than 1.5 rad/W at the frequency of 20 GHz

The electrical properties of metal-insulator-semiconductor structures based on InAs(111)A with thin anodic insulator layers of various thicknesses (7–20 nm) are investigated. It is established that the oxidation of InAs in a fluorinated acid electrolyte results in decreasing density of surface states and fixed charge in the anodic layer to values of < 2 × 1010 cm−2 eV−1 and ∼3 × 1011 cm−2, respectively. Comparison of the electrical parameters with the chemical composition of the layers shows that an improvement in the parameters of the fluorinated anodic oxide/InAs(111)A interface is caused by the substitution of oxygen atoms for fluorine in the anode layers with the formation of indium and arsenic oxifluorides and In-F bonds on the InAs surface.

Composition and electrical characteristics of HfO 2 /Si/GaAs(001) interface formed by e-beam evaporation of Hf in NO 2 ambient on MBE-grown Si/GaAs structure, were studied by XPS and C-V methods. The deposition of HfO 2 on Si-passivated GaAs(001) surface leads to the formation of sharp HfO 2 /Si/GaAs interface without oxidation of Si interlayer. AFM studies of the HfO 2 /Si/GaAs(001) interface show that HfO 2 deposition preserved the flatness of the surface, keeping the mean roughness on the terraces on a level of approximately 0.2–0.3 nm.

Parameters of Schottky barrier diodes (SBD), such as the ideality factor (n), series resistance (R s ) and the effective barrier height (ϕ Bn ), were obtained from I-V and C-V measurements of Al/Si/GaAs and Al/GaAs heterostructures at room temperature. For SBD with a Si interlayer grown by molecule beam epitaxy the following parameters were found: n = 1.29, ϕI-V = 0.74eV and R s = 120Ω as compared to the sample without interlayer (1.7–7.5, 0.8eV and 500Ω, respectively). The electronic properties of Si/GaAs(001) interface were determined from C-V and G-V measurements of Al/SiO 2 /GaAs (001) MIS structure. It is shown that formation of Si/GaAs(001) interface allows reducing the density of surface states to ∼(1–5)·1011 cm−2 eV−1 for Au/SiO 2 /GaAs (001) MIS structure.

We developed and applied a method of InAs passivation in the low-energy plasma of Townsend discharge. The controlled interface oxidation in the Ar:O2:CF4 gas mixture under visualization of gas discharge plasma allowed growing thin homogeneous films in the range of 5–15 nm thickness. Oxidation with the addition of CF4 in gas-discharge plasma led to the formation of In and As oxyfluorides with a wide insulating gap and isostructural interface with unpinned Fermi level behavior. The metal-oxide-semiconductor structure showed excellent capacitance-voltage characteristics: small frequency dispersion (

The influence of electron energy quantization in a space-charge region on the accumulation capacitance of the InAs-based metal-oxide-semiconductor capacitors (MOSCAPs) has been investigated by modeling and comparison with the experimental data from Au/anodic layer(4-20 nm)/n-InAs(111)A MOSCAPs. The accumulation capacitance for MOSCAPs has been calculated by the solution of Poisson equation with different assumptions and the self-consistent solution of Schrodinger and Poisson equations with quantization taken into account. It was shown that the quantization during the MOSCAPs accumulation capacitance calculations should be taken into consideration for the correct interface states density determination by Terman method and the evaluation of gate dielectric thickness from capacitance-voltage measurements.

In this letter, we present electrical and magnetic characteristics of HfO2-based metal-oxide-semiconductor capacitors (MOSCAPs), along with the effect of pseudomorphic Si as a passivating interlayer on GaAs(001) grown by molecular beam epitaxy. Ultrathin HfO2 high-k gate dielectric films (3–15 nm) have been grown on Si/GaAs(001) structures through evaporation of a Hf/HfO2 target in NO2 gas. The lowest interface states density Dit at Au/HfO2/Si/GaAs(001) MOS-structures were obtained in the range of (6−13)×1011 eV−1 cm−2 after annealing in the 400–500 °C temperature range as a result of HfO2 crystallization and the Si layer preservation in non-oxidized state on GaAs. HfO2-based MOSCAPs demonstrated the ferromagnetic properties which were attributed to the presence of both cation and anion vacancies according to the first-principle calculations. Room-temperature ferromagnetism in HfO2 films allowed us to propose a structure for the ferromagnetic MOS spin-detector.

The mechanisms of diffusion via grain boundaries in two-dimensional metals have been studied by method of molecular dynamics. It is established that the diffusion can proceed by two mechanisms, which results in deviations from the Arrhenius law. The first mechanism is related to the formation of chains of atomic displacements between two dislocation cores along the boundary (for high-angle boundaries, between the regions of contraction and extension); the second mechanism consists in a cyclic exchange of atomic sites near the same dislocation core (for high-angle boundaries, near the defect region).