Light-emitting III–N heterostructures are grown by gas-phase epitaxy from organometallic compounds on SiC/Si (111) templates (substrates) formed using matched atomic substitution. Investigations of the optical and structural properties of heterostructures are carried out in order to reveal the formation of defects in the structures. It is shown that such heterostructures exhibit specific features of the growth of the (Al,Ga)N buffer layer associated with the presence of pores in Si under the SiC/Si interface. The use of an optimized buffer layer design makes it possible to significantly reduce the dislocation density and form an active region with good structural quality.

We have studied the growth of GaN layers by the metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates at various reactor pressures, including ones above the atmospheric level. It is established that the epitaxial growth at higher pressures does not affect the crystalline perfection of epilayers, their electron mobility, and background impurity level, but leads to the formation of GaN surface with lower lateral scale of inhomogeneities. In addition, the reactor pressure influences the ratio of edge and impurity lines in the photoluminescence spectra and leakage current level in reversely biased Schottky barriers.

Light emitting III-N heterostructures were grown by metalorganic chemical vapor deposition on the SiC/Si (111) templates (substrates) formed by the method of matched substitution of atoms. Investigations of the optical and structural properties of heterostructures were carried out in order to reveal the formation of defects in the structures. It is shown that features of the growth of the (Al, Ga)N buffer layers in such structuresare associated with the presence of pores in the Si substrate under SiC/Si interface. Applying of the optimal design of the buffer layer allows significantly reduce the dislocation density and form active region with high structural quality.

Growth of GaN layers by MOVPE on sapphire substrates at various pressures, including above atmospheric, was studied. It is shown that epitaxy at higher pressures does not change the crystal perfection of the layers, the electron mobility, and the impurities incorporation, but leads to the formation of a surface with a smaller lateral scale of inhomogeneities. The epitaxy pressure also affects the ratio of the intensity of the band-edge and impurity-related lines in the photoluminescence spectra and the leakage currents in the reverse-biased Schottky barrier.

InGaN-based dichromatic light emitting diodes (LEDs) emitting in the blue and cyan spectral ranges simultaneously, are investigated both experimentally and theoretically. Two main approaches to controlling the ratio of blue-to-cyan components in the emission spectrum are suggested and analyzed: (i) thickness variation of the GaN barrier between the blue and cyan quantum wells and (ii) optimization of the barrier doping with n- or p-type impurities. Detailed examination of the approaches is carried out in order to understand their capabilities for intentional variation of the blue-to-cyan ratio in a wide range. Based on numerical simulations, a novel mechanism, invoking enhanced Shockley-Read-Hall recombination in the barrier and underlying both approaches, is suggested and discussed. It is shown that proposed design of the monolithic blue-cyan LEDs does not result in substantial decrease of the LED emission efficiency compared to monochromatic blue or cyan reference samples.

A significant difference in the growth mechanism of spatially closed structures of gallium nitride during selective growth in submicron windows with and without penetration into the GaN sublayer was demonstrated. The mechanisms of generation and development of dislocations, their role in the formation of self-organizing coaxial structures were modeled.

The effect of annealing temperature and time on the luminescence intensity of the InGaN/GaN heterostructure subjected to ion beam etching was studied. We show that annealing at a temperature of 1100°C makes it possible to eliminate the radiation defects in the GaN layers that arise in the etching process with a focused Ga+ ion beam (30 keV).

InAlN/AlN/GaN semiconductor heterostructures with a barrier thickness of 5–13 nm have been grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire and SiC substrates. Optimization of GaN buffer and InAlN layers allows fabricating structures with sheet conductivity values below 210 Ohm/sq. High electron mobility transistors (HEMTs) fabricated from such structures show drain current value exceeding 1.25 A/mm with maximum transconductance of 450 mS/mm. Use of thin in situ Si3N4 capping allows to fabricate and compare HEMT and MIS-HEMTs.

AbstractThe selective epitaxial growth of GaN by metalorganic vapor-phase epitaxy combined with ion-beam etching is investigated. To this end, partially masked GaN epitaxial layers are fabricated by depositing a thin Si_3N_4 layer onto the surface in a single technological process with the growth of GaN and the subsequent opening of windows of different shapes in this layer by an ion beam. Selective epitaxial growth regimes are studied. It is shown that, in a situation where the total area of the windows in the mask is small relative to the total area of the sample, the required epitaxy duration should be 5–10 s, which impairs the reproducibility of the parameters of the epitaxial process. It is also shown that the mechanism of the selective growth of submicrometer objects differs significantly from that for planar layers and selectively grown layers with dimensions of ~1 μm or greater. The effect of precursor (trimethylgallium and ammonia) fluxes on the character of selective epitaxy is examined. To investigate the possibilities of varying mask topology for fabricating model objects with regard to photonic crystals, the impact of the shape and orientation of the windows in the Si_3N_4 mask on the character of selective epitaxy is studied.

Dependence of electroluminescence spectrum shape of blue-cyan InGaN-based dichromatic double quantum well light emitting diodes on the thickness and doping level of the barrier between quantum wells was investigated numerically and experimentally.

Optical properties of the resonant Bragg heterostructures with 10 and 30 GaN/AlGaN quantum wells were studied. The increasing of reflectivity at the resonance wavelength under condition of the Bragg wavelength and optical transition wavelength matching was observed experimentally at room temperature. The computer simulation of the optical transition wavelength in quantum wells and the optical reflectivity spectra at different reverse bias was implemented to evaluate radiative and non-radiative broadening parameters of the exciton in GaN/AlGaN quantum wells.

Optical and structural properties of thick InGaN layers grown by MOCVD and MBE were studied by photoluminescence, optical transmission and Raman spectroscopies and X-ray diffraction analysis. Optical bandgap, Urbach energy, and full widths at half maximum ( FWHM) of photoluminescence and Raman spectra depending on the InGaN alloy composition were determined experimentally. Minimal theoretical linewidth of photoluminescence spectra resulted from random distribution of In and Ga atoms in cation sublattice was calculated.

The selective epitaxial growth of GaN by metalorganic vapor-phase epitaxy combined with ion-beam etching is investigated. To this end, partially masked GaN epitaxial layers are fabricated by depositing a thin Si3N4 layer onto the surface in a single technological process with the growth of GaN and the subsequent opening of windows of different shapes in this layer by an ion beam. Selective epitaxial growth regimes are studied. It is shown that, in a situation where the total area of the windows in the mask is small relative to the total area of the sample, the required epitaxy duration should be 5–10 s, which impairs the reproducibility of the parameters of the epitaxial process. It is also shown that the mechanism of the selective growth of submicrometer objects differs significantly from that for planar layers and selectively grown layers with dimensions of ~1 μm or greater. The effect of precursor (trimethylgallium and ammonia) fluxes on the character of selective epitaxy is examined. To investigate the possibilities of varying mask topology for fabricating model objects with regard to photonic crystals, the impact of the shape and orientation of the windows in the Si3N4 mask on the character of selective epitaxy is studied.

Microcrystalline wire-like InGaN/GaN light-emitting diodes designed as core–shell structures 400–600 μm in length are grown by metal–organic vapor-phase epitaxy on sapphire and silicon substrates. The technology of the titanium-nanolayer-induced ultrafast growth of nanowire and microwire crystals is used. As a current is passed through the microcrystals, an electroluminescence signal is observed in the blue–green spectral region.

The series of InAlGaN LED structures containing two different quantum wells emitting at wavelengths of similar to 430 nm and similar to 490 nm was grown. The influence of the quantum wells order, thickness of the barrier between the wells and its doping level on the optical properties was studied by photo- and electro-luminescence measurements. It was found that the quantum well with longer-wavelength emission is preferable to be located farther from a player than the shorter-wavelength quantum well to obtain emission from both QWs. Variation of the thickness of the barrier between the QWs and its doping level allows controlling the intensity ratio of two emission peaks.

Нитевидные микрокристаллические светодиодные структуры InGaN/GaN в геометрии ядро--оболочка длиной 400-600 мкм были выращены методом газофазной эпитаксии из металлоорганических соединений на сапфировых и кремниевых подложках. Использовалась технология сверхбыстрого роста нитевидных нано- и микрокристаллов, индуцированного нанослоем титана. При протекании тока наблюдалась электролюминесценция микрокристаллов в сине-зеленом спектральном диапазоне. DOI: 10.21883/FTP.2017.01.8293

The results of development of InAlN/AlN/GaN heterostructures, grown on sapphire substrates by metal-organic chemical vapour deposition, and high electron mobility transistors (HEMTs) based on them are presented. The dependencies of the InAlN/AlN/GaN heterostructure properties on epitaxial growth conditions were investigated. The optimal indium content and InAlN barrier layer thicknesses of the heterostructures for HEMTs were determined. The possibility to improve the characteristics of HEMTs by in-situ passivation by Si3N4 thin protective layer deposited in the same epitaxial process was demonstrated. The InAlN/AlN/GaN heterostructure grown on sapphire substrate with diameter of 100 mm were obtained with sufficiently uniform distribution of sheet resistance. The HEMTs with saturation current of 1600 mA/mm and transconductance of 230 mS/mm are demonstrated.

InGaN‐based monolithic multi‐color light emitting diodes (LEDs) are studied both experimentally and theoretically with the focus on factors controlling their emission spectra and efficiency. A number of LEDs with different designs of spacers separating active regions providing blue and green light emission is examined. Unexpected behavior of the multi‐color LED efficiency is explained in terms of a simple balance model, assuming some degradation of materials quality of the green active region grown on top of the blue one. Electrical properties of spacers separating different active regions in the multi‐color LED structures are identified as the major factor controlling the contributions of these active regions to the total emission spectrum. Correlations between the type and level of the spacer doping and the emission spectrum are found by simulations. Alternative ways of the spectral control by using polarization doping in the graded‐composition InGaN and AlGaN alloys used as the spacers are suggested. Color characteristics of blue/green dual‐wavelength LEDs are also measured and discussed, regarding their possible applications.

The impact of electromechanical coupling on optical properties of light-emitting diodes (LEDs) with InGaN/GaN quantum-dot (QD) active regions is studied by numerical simulations. The structure, i.e. the shape and the average In content of the QDs, has been directly derived from experimental data on out-of-plane strain distribution obtained from the geometric-phase analysis of a high-resolution transmission electron microscopy image of an LED structure grown by metalorganic vapor-phase epitaxy. Using continuum [Formula: see text] calculations, we have studied first the lateral and full electromechanical coupling between the QDs in the active region and its impact on the emission spectrum of a single QD located in the center of the region. Our simulations demonstrate the spectrum to be weakly affected by the coupling despite the strong common strain field induced in the QD active region. Then we analyzed the effect of vertical coupling between vertically stacked QDs as a function of the interdot distance. We have found that QCSE gives rise to a blue-shift of the overall emission spectrum when the interdot distance becomes small enough. Finally, we compared the theoretical spectrum obtained from simulation of the entire active region with an experimental electroluminescence (EL) spectrum. While the theoretical peak emission wavelength of the selected central QD corresponded well to that of the EL spectrum, the width of the latter one was determined by the scatter in the structures of various QDs located in the active region. Good agreement between the simulations and experiment achieved as a whole validates our model based on realistic structure of the QD active region and demonstrates advantages of the applied approach.

The effect of the layer thickness and composition in AlGaN/AlN/GaN and InAlN/AlN/GaN transistor heterostructures with a two-dimensional electron gas on their electrical and the static parameters of test transistors fabricated from such heterostructures are experimentally and theoretically studied. It is shown that the use of an InAlN barrier layer instead of AlGaN results in a more than twofold increase in the carrier concentration in the channel, which leads to a corresponding increase in the saturation current. In situ dielectric-coating deposition on the InAlN/AlN/GaN heterostructure surface during growth process allows an increase in the maximum saturation current and breakdown voltages while retaining high transconductance.