F. A. Luk’yanov

Luminescence spectra, efficiency, and color characteristics of white-light-emitting diodes based on p-n InGaN/GaN heterostructures with phosphor coatings

The luminescence spectra, efficiency, and color characteristics of white-light-emitting diodes fabricated from p-n InGaN/AlGaN/GaN blue-light-emitting heterostructures grown on SiC substrates and coated with yellow-green phosphors based on the rare-earth-doped yttrium-aluminum garnets were studied. The efficiency of blue-emitting diodes is as high as 22% at a current of 350 mA and a voltage of 3.3 V. The white-emitting diodes have luminous efficiency as high as 40 lm/W and luminous flux up to 50 lm at 350 mA.

Fianite: A multipurpose electronics material

Fianite-zirconium dioxide, stabilized by yttrium (YSZ) has a unique combination of physical and chemical properties that made it a very promising material for a wide range of applications. In this work, we consider the use of fianite as a bulk substrate and buffer layer for AIIIBV epitaxy, and as an antireflection and protective coating for photo detectors and solar cells.

Increasing spatial resolution in the backscattered electron mode of scanning electron microscopy

A new method for increasing spatial resolution in the detection of backscattered electrons and induced current in scanning electron microscopy (SEM) is proposed in terms of regularized Fourier transform. The real size of an electron probe and its blurring in a solid target sample are considered in forming the algorithm. The experiments reveal an almost 100% improvement in resolution in the processed images.

A method and devices of electron microtomography in scanning electron microscopy

A method of microtomography of layered microstructures during detection of backscattered electrons in a scanning electron microscope is described. This method is based on the formation of layer-by-layer images hidden under the surfaces of microstructures using reflected electrons filtered within a narrow energy window. An improved deflector-type spectrometer with toroidal electrostatic sector electrodes is applied for microtomography and spectroscopy. To improve the sharpness and accuracy of separation of individual buried heteroboundaries, the modulation principle of video-signal detection is implemented.

Characterization of semiconductor detectors of (1–30)-keV monoenergetic and backscattered electrons

Semiconductor detectors of backscattered electrons are basic elements of all modern scanning electron microscopes. Their quality is determined by the properties of planar p-n junctions and the parameters of the protective layer on the detector surface. The main characteristics of semiconductor detectors are considered, their response functions are calculated, and the threshold signal cutoff energies are found both for a monoenergetic electron beam and for detection of the total energy spectrum of backscattered electrons. The experimental results are in good agreement with the computational model data.

Determination of the mean energy of backscattered electrons in dependence on the exit angle

A semiconductor detector was used to measure the mean energy of backscattered electrons as a function of the exit angle. New regularities of electron backscattering were found. A nonmonotonic dependence of the mean energy of backscattered electrons on the exit angle and the primary electron energy for materials with different atomic numbers was revealed.

Heteroepitaxial III–V films on fianite substrates and buffer layers

GaAs, GaSb, AlGaAs, and InGaAs epitaxial films and multilayer AlGaAs/InGaAs/GaAs heterostructures for PHEMT field-effect transistors have been obtained on fianite substrates by metal-organic vapour phase epitaxy. Films of different III–V compounds, including GaN, were grown on Si and GaAs substrates with a simple single buffer layer (fianite) and double buffer layer (fianite on porous Si and GaAs). It is established that the use of a two-layer buffer improves the structural quality and homogeneity of III–V films. A possibility of controlling the phase composition of GaN films using a corresponding buffer layer is shown. It is found that the use of a two-layer buffer increases the electrical homogeneity and decreases the electrical activity of defects in GaN films.

Epitaxial films of GeSi, AlGaN, and GaSb and GaSb/InAs superlattices on substrates of fianite

Fianite is a single crystal of cubic solid solutions based on zirconium dioxide (ZrO2) or hafnium dioxide (HfO2) with stabilizing oxides of yttrium, scandium, and lanthanides. It is characterized by a unique combination of physical and chemical properties, making it a promising material for wide use in electronics. In this work, we consider new uses of fianite as a monolith substrate for obtaining Ge, GeSi, AlGaN, and GaSb epitaxial films and GaSb/InAs superlattices.

Energy Spectra of Electrons Backscattered from Bulk Solid Targets

Energy distribution spectra of backscattered electrons in the range 5–25 keV are obtained experimentally. An inverse problem of the reconstruction of the true electron spectrum is solved taking into account the instrument response function of the spectrometer; on the basis of the obtained solution, we specify functions of the real energy distribution of the electrons backscattered from homogeneous and layered samples.

Heteroepitaxial GaN films on silicon substrates with porous buffer layers

New complex buffer layers based on a porous material have been developed for epitaxial growth of GaN films on Si substrates. The characteristics of gallium nitride heteroepitaxial layers grown on silicon substrates with new buffer layers by metal-organic vapor phase epitaxy are investigated. It is shown that the porous buffer layers improve the electric homogeneity and increase the photoluminescence intensity of epitaxial GaN films on Si substrates to the values comparable with those for reference GaN films on Al2O3 substrates. It is found that a fianite layer in a complex buffer is a barrier for silicon diffusion from the substrate into a GaN film.