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we present the results of fabrication of flip-chip LEDs with removed substrate from AlInGaN heterostructures grown on SiC/Si substrates synthesized by vacancy-matching atom substitution. It is shown that SiC/Si substrates are optimal from the viewpoint of matching lattice parameters, thermal conductivity, and optical characteristics of the material at a significantly lower cost. Therewith, the procedure of cutting wafers into individual chips and removal of the opaque silicon part of the substrate becomes easier, and the transparent SiC part of the substrate remaining on the chip surface creates a relief that facilitates light output. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of substrate for manufacturing LEDs based on AlInGaN heterostructures. Instead of depositing SiC layers on the surface of Si using the conventional method, a new method involving the coordinated substitution of atoms (MCSA) to form the SiC layer is proposed. This new approach enables the growth of epitaxial GaN layers with low defect content and facilitates transfer to any surface. The paper details the technology of manufacturing LEDs on SiC/Si substrates obtained by the MCSA and elaborates on the benefits of using these substrates in LED production. Additionally, the advantages of the growth interface between SiC and Si materials are discussed. Moreover, it is found that thinner SiC layers (<200 nm) contribute to the scattering of the LED's own radiation in the heterostructure waveguide, which decreases its absorption by silicon. For flip-chip LEDs with the substrate removed, substrates with thicker SiC layers (~400 nm) and a growth porous layer of several microns at the SiC-Si interface is utilized to simplify Si substrate removal and enhance the manufacturing process's cost-effectiveness. [ABSTRACT FROM AUTHOR]

The results of the study of the influence of Fe segregation into the unintentionally doped GaN channel layer in AlGaN/AlN/GaN heterostructures with Fe-doped GaN buffer layer on the electrical properties of two-dimensional electron gas are presented. A set of several samples was grown by metal-organic vapor-phase epitaxy and characterized by the van der Pauw method. The dependence of concentration and mobility of the two-dimensional electron gas on the channel layer thickness was analyzed theoretically by self-consistent solving of 1D Poisson and Schrödinger equations and scattering rate calculations within the momentum relaxation time approximation. It was found that both concentration and mobility decreases were responsible for the increase in the sheet resistance in the structures with a thinner channel layer, with a drop in mobility being not only due to ionized impurity scattering, but also due to a combined effect of weakening of screening, lower carrier energy and change in form-factors on scattering by interface roughness, dislocations and polar optical phonons. [ABSTRACT FROM AUTHOR]

A technique and technology for manufacturing both LED chips and packaged LEDs from AlInGaN/GaN heterostructures grown on novel SiC/Si substrates synthesized by the method of matched substitution of atoms is described. We have studied the current-voltage characteristics, electroluminescence spectra, and dependence of output power and external quantum efficiency on the current. It is shown that the presence of pores in the SiC/Si substrate, which are naturally formed during its growth, leads to a significant increase in the quantum efficiency of LEDs compared with the quantum efficiency of LEDs fabricated on silicon without a SiC sublayer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Features of plasma-assisted molecular-beam epitaxy of AlGaN compounds at relatively low temperatures of the substrate (no higher than 740°C) and various stoichiometric conditions for growth of the nitrogen- and metal-enriched layers are studied. Discrete submonolayer epitaxy for formation of quantum wells and n-type blocking layers without varying the fluxes of components was used for the first time in the case of molecular- beam epitaxy with plasma activation of nitrogen for the nanostructures with the Al x Ga1 − x N/Al y Ga1 − y N quantum wells. Structural and optical properties of the Al x Ga1 − x N layers in the entire range of compositions ( x = 0–1) and nanostructures based on these layers are studied; these studies indicate that there is photoluminescence at room temperature with minimum wavelength of 230 nm. Based on the analysis of the photoluminescence spectra for bulk layers and nanoheterostructures and their temperature dependences, it is concluded that there are localized states in quantum wells. Using the metal-enriched layers grown on the c-Al2O3 substrates, heterostructures for light-emitting diodes with Al x Ga1 − x N/Al y Ga1 − y N quantum wells ( x = 0.4–0.5, y = x + 0.15) were obtained and demonstrated electroluminescence in the ultraviolet region of the spectrum at the wavelength of 320 nm. [ABSTRACT FROM AUTHOR]

InGaN/GaN structures with dense arrays of InGaN nanodomains were grown by metallorganic chemical vapor deposition. Lasing in vertical direction occurs at low temperatures, indicating ultrahigh gains (∼10[sup 5] cm[sup -1]) in the active region. Fabrication of an effective AlGaN/GaN distributed Bragg reflector with reflectivity exceeding 90% enables vertical lasing at room temperature in structures with a bottom distributed Bragg reflector, despite the absence of a well-reflecting upper mirror. The lasing wavelength is 401 nm, and the threshold excitation density is 400 kW/cm². [ABSTRACT FROM AUTHOR]

Lasing is discovered in the direction perpendicular to the surface in quantum-size InGaN/GaN multilayer heterostructures grown by vapor-phase epitaxy. At high excitation densities one of the modes in the luminescence spectrum, which is modulated by modes of the Fabry-Pérot cavity formed by the GaN/air and GaN/sapphire-substrate interfaces, is sharply amplified and begins to dominate the spectrum. The dependence of the luminescence intensity on pump density has a clearly expressed threshold character. The threshold excitation density in the vertical direction is 5-6 times greater than the stimulated-emission threshold for observation from an end surface of the structure. The gain coefficient in the active region at the threshold for surface-emitting lasing is estimated as 2 × 10[sup 5] cm[sup -1]. The interaction between the cavity modes and the gain spectrum is detected in the form of displacement (by up to 2.6 nm) of modes on the short-wavelength edge of the luminescence spectrum toward higher photon energies. The characteristic temperature (T[sub 0]) measured in the range from 16 to 120 K is 480 K. At higher temperatures T[sub 0] = 70 K. [ABSTRACT FROM AUTHOR]

Semiconductor heterostructures with vertical optical cavities with active regions, based on arrays of InAs quantum dots inserted in an external InGaAs quantum well, have been obtained by molecular-beam epitaxy on GaAs substrates. The dependences of the reflection and photoluminescence spectra on the structural characteristics of the active region and optical cavities have been investigated. The proposed heterostructures are potentially suitable for optoelectronic devices at wavelengths near 1.3 µm. [ABSTRACT FROM AUTHOR]

It is shown that the self-organization effects appearing during the N-cycle deposition of In[sub 0.5]Ga[sub 0.5]As(12 Å)/GaAs(50 Å) lead to the formation of ordered arrays of vertically coupled quantum dots (VCQD's). The optical properties are investigated as a function of the number of deposition cycles (N = 1-10). In cases of injection heterostructure lasers with an active region based on VCQD's it is shown that increasing the number N of deposition cycles from 1 to 10 makes it possible to lower the threshold current density at 300 K from 950 to 97 A/cm² and to achieve a continuous lasing regime at room temperature with an output power of 160 mW per mirror. [ABSTRACT FROM AUTHOR]

In the present paper we report on the observation and study of intense spontaneous THz emission from modulation-doped AlGaN/GaN heterostructure under conditions of heating of two-dimensional electron gas in lateral electric field. The experimental results are compared with the model of blackbody-like thermal emission of hot 2D electrons. Complementary transport measurements and theoretical simulation were carried out to determine the dependence of effective electron temperature on electric field. The role of non-equilibrium optical phonon accumulation is discussed. [ABSTRACT FROM AUTHOR]

One of the main factors that limit the maximum attainable efficiency of InGaAlN-based light-emitting diode (LED) structures grown on standard sapphire substrates is the low efficacy of extracting light from devices. A promising solution of this problem consists in using specially profiled (patterned) sapphire substrates. A method for the formation of a special surface microrelief on the sapphire substrates is described. The properties of GaN epilayers and InGaAlN-based LED heterostructures grown on such substrates are presented. [ABSTRACT FROM AUTHOR]

The behavior of threading dislocations in AlGaN and InGaN layers incorporated into GaN-based heterostructures is studied. It is shown that InGaN layers with an intermediate composition can be used as the most effective dislocation filters. Estimations of the stresses generated by dislocations and nanodomains show good agreement between the theory and experiment. [ABSTRACT FROM AUTHOR]

Specific features of MOCVD growth of AlGaN/GaN heterostructures have been studied. In the structures obtained, the 2D electron gas in the channel had a density of 1.2 × 1013cm–2 and a mobility of 1290 cm2/(V s) at room temperature. The effect of the purity of starting components on the properties of the structure is studied. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The influence of different growth conditions on the In distribution in ultrathin InGaN insertions in a GaN matrix is investigated by high-resolution transmission electron microscopy and an appropriate image evaluation technique. It is demonstrated that the indium distribution represents dense arrays of In-rich nanodomains inserted in a layer with a lower indium concentration. The sizes of the In-rich regions are about 4-5 nm at a growth temperature of 720 °C. Increasing the growth temperature leads to a strong decrease in the of nanoisland density and, also, a moderate decrease in their lateral size. Increasing the trimethylindium/trimethylgallium ratio strongly increases the density of the islands, but the lateral size remains weakly effected. The observations are in agreement with a thermodynamic model of island formation including entropy effects. [ABSTRACT FROM AUTHOR]

The luminescence properties of a GaN/A1[sub 0.1]Ga[sub 0.9]N double heterostructure grown by vapor-phase deposition from organometallic compounds are studied. When luminescence is observed from the end, the radiation intensity shows a sharply defined threshold dependence on the pump density. The threshold excitation density at T = 77 K was ∼40 kW/cm² and the wavelength of the stimulated emission was λ = 357 nm. The long-wavelength shift of the emission line at high pump densities may be attributed to renormalization of the band gap caused by manyparticle interactions in the electron-hole plasma. [ABSTRACT FROM AUTHOR]