Search

Emission-voltage characteristics and frequency dependences of the luminescence intensity of electroluminescent capacitors on the basis of the ZnS:(Cu,Al) phosphor are studied. The effect of X-ray radiation (17 keV) on the high-resistivity GaAs layers obtained by three methods is studied. The possibility to develop the detectors of the ionizing radiation with optical reading of information with the use of the GaAs/ZnS structures is shown using a mathematical simulation. It is noted that the most promising material for the development of the solid-state image converters is GaAs:Cr obtained by diffusion of Cr from the deposited layer. [ABSTRACT FROM AUTHOR]

The quantum theory of the accumulation layer for n-type InN crystals is developed. The Coulomb interaction and the exchange interaction in the Kohn-Sham local density approximation is considered. The applicability of the theory is demonstrated by using recent literature data. The approach developed provides more solid data on the accumulation layer parameters. [ABSTRACT FROM AUTHOR]

The N-Al0.27Ga0.73N/GaN High Electron Mobility Transistors (HEMTs) with different gate lengths L g (ranging from 170 nm to 0.5 μm) and gate widths W s (ranging from 100 to 1200 μm) have been studied. The S parameters have been measured; these parameters have been used to determine the current-gain cutoff frequency f t, the maximum oscillation frequency fmax, and the power gain MSG/MAG and Mason’s coefficients were investigated in the frequency range from 10 MHz to 67 GHz in relation to the gate length and gate width. It was found that the frequencies f t and fmax attain their maximum values of f t = 48 GHz and fmax = 100 GHz at L g = 170 nm and W g = 100 μm. The optimum values of W g and output power P out of the basic transistors have been determined for different frequencies of operation. It has also been demonstrated that the 170 nm Al0.27Ga0.73N/GaN HEMT technology provides both good frequency characteristics and high breakdown voltages and is very promising for high-frequency applications (up to 40 GHz). [ABSTRACT FROM AUTHOR]

Using the Hall method, regularities of Te doping of GaSb grown by the Czochralski method and by liquid-phase epitaxy (LPE) are studied. Optimum epitaxial conditions that enable the growth of Te-doped GaSb layers with higher carrier mobilities than the bulk Czochralski-grown GaSb are determined. Possibilities of improvement of output parameters of photoconverters obtained by diffusion of Zn into n-GaSb from the gas phase and by LPE are discussed. [ABSTRACT FROM AUTHOR]

The pseudomorphic AlGaAs/InGaAs/AlGaAs heterostructure δ-doped with silicon on both sides and used for fabrication of high-power transistors is optimized to obtain a high concentration n s and mobility of two-dimensional electron gas in the quantum well ( n s ≈ 3 × 1012 cm−2). Electrical and structural characteristics of the samples grown by molecular-beam epitaxy with various doping levels are studied. It is shown that the mobility and concentration of electrons varies as doping level is increased and the subbands of dimensional quantization are sequentially filled. In order to analyze the distribution of electrons in subbands of the heterostructure, the Shubnikov-de Haas oscillations at the liquid helium temperature were studied. The quality of the heterostructure layers was assessed using the method of X-ray diffraction. The data of photoluminescence spectroscopy are in good agreement with the results of calculations of the band structure. [ABSTRACT FROM AUTHOR]

Using the method of atomic force microscopy, complex studies of the profile, potential distribution φ( x, y), and distributions of the phase contrast of the surface of n-GaAs subjected to various types of chemical treatment are carried out. The distribution of the potential and phase contrast at a microlevel, in general, correlates with the profile character. The surface treated in the solution H2SO4: H2O = 1: 10 is characterized by a high degree of nonuniformity with an average roughness of the main profile Δ h≈ 10 nm. A considerable part of the surface is covered by hills 20–60 nm in height and 100–500 nm in diameter forming a specific substructure, which correspond to potential jumps as large as 50–60 mV against a general background of 0.77–0.80 V. At a nanolevel, correlation between the profile and phase contrast is clearly pronounced, but no correlation is found between the profile and potential distribution. Treatment of the surface of n-GaAs in a concentrated aqueous NH4OH solution leads to a decrease in the value of φ( x, y) by ∼0.2 V, and in its roughness by more than an order of magnitude (∼0.75 nm). The distribution of the profile and phase contrast over the surface is close to the ideal Gaussian distribution for relatively small areas of the surface (200 × 200 nm2). As the area increases, deviation from the Gaussian distribution becomes substantial because of smooth variation in the potential over the contact area. Conservation of the Gaussian character of the surface profile and a simultaneous rise in the average level of the roughness with an increase in the analyzed area indicates the fractal mechanism of formation of the surface profile. [ABSTRACT FROM AUTHOR]

Morphological and optical (with reflection spectra in the range of 200–750 nm, transmission spectra in the range of 2–25 μm, and ellipsometry) studies were performed for AlN films that had a thickness of 2–3 μm and were obtained by the method of high-frequency magnetron sputtering of an aluminum target in a gas mixture of Ar and N2 (1: 3) with deposition onto single-crystal n-Si (100) substrates with a resistivity of 20–60 Ω cm. It is shown that the films are dense and transparent; they are amorphous with crystalline grains and can be used efficiently in thin-film technology for fabrication of modern microelectronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Based on the measurements of current-voltage and capacitance-voltage characteristics and deep-level transient spectroscopy, comparison of the concentration of deep-level centers and conductivity of the channel of the AlGaN/GaN heterostructures grown by molecular beam epitaxy with the use of ammonia as the nitrogen source is carried out. Two types of defects with deep levels are revealed. One type is presumably associated with point defects localized near dislocations, and the other type is associated with the dislocations themselves. An increase in the concentration of the centers with deep levels correlates with an increase in the channel resistivity. The density of the deep-level centers can attain values of ∼1013 cm−2 and lead to compensation of the electron channel at the heterointerface. [ABSTRACT FROM AUTHOR]

GaAs layers doped by implantation of Mn and Mg ions to increase the hole concentration were synthesized and studied. Measurements using a SQUID magnetometer showed that there is ferromagnetism at temperatures as high as 400 K, which is related to the formation of the MnAs and Mn y Ga1 − y clusters as a result of high-temperature annealing, in addition to the formation of the Ga1 − x Mn x As alloy. The anomalous Hall effect was observed at temperatures in the range from 4.2 to 200 K. As temperature was increased starting with 4.2 K, the negative magnetoresistance with extremely large magnitude transformed into a giant positive magnetoresistance at T ≈ 35 K. [ABSTRACT FROM AUTHOR]

The effect of growth temperature of the AlGaAs spacer layer on mobility in a two-dimensional electron gas μ e in single-side δ-doped pseudomorphic AlGaAs/InGaAs/GaAs transistor structures with a high electron mobility is studied experimentally. The energy-band diagram is analyzed using a self-consistent calculation. In order to study the electronic transport properties, an optimized structure in which there is no parallel conduction over the doped layer was chosen. It is shown that, in optimized structures, the mobility μ e increases by 53% at T = 300 K and by 69% at T = 77 K as the growth temperature increases from 590 to 610°C, with the other parameters and the growth conditions remaining the same. It is assumed that this behavior is related to an improvement in the structural quality of the AlGaAs spacer layer and the AlGaAs/InGaAs/GaAs heteroboundary. [ABSTRACT FROM AUTHOR]

The energy and wave functions of localized electron states in a quantum well in a high magnetic field arbitrarily oriented with respect to the layers of the structure, and a high transverse electric field are studied. The situation where the quantum-confined energy and the Landau energy are close to each other is considered. The evolution of the spectrum with varying orientation of the magnetic field over the entire angle range is studied. [ABSTRACT FROM AUTHOR]

To find the parameters of low-barrier Schottky diodes, a diagnostics technique based on an analysis of the dependence of the differential resistance of a diode with a Mott barrier and near-surface δ-shaped doping is developed. It is shown that a complete description of the current-voltage characteristics of the diode is possible with regard to the series n −- n + junction. The technique makes it possible to optimize diodes to attain higher detection sensitivity. [ABSTRACT FROM AUTHOR]