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Low-temperature circularly polarized electroluminescence in InGaAs/GaAs/δ-〈Mn〉 heterostructures has been studied. It is established that the degree of circular polarization weakly depends on spatial separation of the active region and magnetic layer and is retained even at a spacer layer thickness of 12 nm. The observed phenomenon is related to the long-range magnetic interaction of carriers and Mn ions.

—Spin light emitting diodes (spin-LEDs) containing (Ga,Mn)As ferromagnetic layers are fabricated based on InGaAs/GaAs heterostructures and studied. We achieve increases in the operating temperatures of our spin-LEDs by subjecting the surface of the structures, prior to depositing an ohmic metal contact, to pulsed laser annealing. The fabricated devices produce circularly polarized electroluminescence when placed in an external magnetic field. The temperatures at which circularly polarized electroluminescence is still observed is raised from 30 K for unprocessed structure to 110 K for laser-annealed structures. The observed effect is linked to an increase in the Curie temperature of the (Ga,Mn)As layer as a result of laser impact.

GaAs light-emitting (LED) and HEMT structures with δ-doped regions, InGaAs/GaAs quantum wells, and surface layers of InAs/GaAs quantum dots were studied by means of the electrochemical capacitance- voltage profiling technique. The concentration depth profiles of free charge carriers were obtained. Charges accumulated in quantum wells and quantum dots, as well as the doping levels of the emitter and δ layers were determined. The band structure and free carrier density distribution over the depth of the samples with different quantum well geometry were simulated. The specific features of electrochemical capacitance- voltage profiling in different heterostructure types are analyzed. A method of integration of capacitance- voltage curves at each etching stage was suggested. This method provides the efficient separation of responses from closely located layers, particularly the quantum well and δ layer.

Circularly polarized luminescence of light-emitting InGaAs/GaAs structures with a delta-doped Mn layer in a GaAs barrier was studied. The structural parameters were varied by different ways, among them are homogeneous and delta-doping with acceptor impurity, and removal of donor doping from the technological process. As it was found, the magnitude and polarity of the degree of circular polarization of luminescence strongly depend on the technological mode chosen. Simultaneous modeling of wave functions of structures highlights a good agreement between the parameters of circularly polarized luminescence and spatial distribution of wave functions of heavy holes relative to the Mn delta-layer.

Optical and transport properties of the heterostructure with the InAs/GaAs quantum dots doped with manganese or chromium atoms in the course of growth using metal-organic vapor phase epitaxy (MOVPE) are analyzed. Circularly polarized luminescence was obtained due to doping of quantum dots with the Mn or Cr atoms. The sign of the degree of circular polarization was found to depend on the dopant. The effect is interpreted using specific features of the radiative recombination in quantum dots in the presence of resident electrons and holes.

The optical properties of InGaAs/GaAs quantum dot heterostructures that are doped by manganese and chromium during growth by Metal-organic vapor phase epitaxy have been studied. Surface topography photoluminescence spectra measurements have demonstrated the possibility of controlling the spectral characteristics of the structure by varying quantum well growth conditions and sizes in the presence of impurity atoms. Research results are explained by the peculiarities of InAs nanoclusters formation on the GaAs surface in the presence of Mn and Cr atoms.

The spin light-emitting diodes based on InGaAs/GaAs heterostructures with a quantum well and an injector in the form of a (Ga,Mn)As ferromagnetic layer have been studied. It has been demonstrated that the efficiency of electron spin injection in the structure with a (Ga,Mn)As/n +-GaAs tunneling barrier can be controlled by varying the parameters of n +-GaAs. The spin injection control mechanisms associated with the thermal activation and tunneling of carriers have been discussed.

The luminescence properties of light-emitting diodes based on GaAs/InGaAs heterostructures containing Mn-doped layers are studied. The dependences of the degree of electroluminescence circular polarization on the growth parameters, specifically, the Mn content and the hole concentration are obtained. A steady increase in the degree of electroluminescence circular polarization and in the Curie temperature of the ferromagnetic structure with increasing hole concentration is observed, and a change in sign of the degree of circular polarization under variations in the Mn content is revealed. The data are interpreted on the basis of well-known models of ferromagnetism in structures based on ferromagnetic semiconductors.

The comparative investigation of circularly polarized electroluminescence in Zener diodes based on InGaAs/n-GaAs/n +-GaAs/GaMnAs and InGaAs/n-GaAs/n +-GaAs/GaMnSb is carried out. It is established that the circularly polarized electroluminescence is associated with the spin injection of electrons from a ferromagnetic semiconductor layer. The luminescence parameters are determined by the properties of these layers. It is shown that the ferromagnetic properties of the GaMnSb layer allow us to obtain circularly polarized emission at room temperature from InGaAs/n-GaAs/n +-GaAs/GaMnSb heterostructures.

Spin injection light-emitting diodes based on heterostructures with InGaAs/GaAs quantum wells and a ferromagnetic metal (Co) contact layer are fabricated and studied. The effect of the penetration of cobalt in GaAs is experimentally detected. It is demonstrated that the use of tunnel-thin (1–3 nm) Al2O3 layers as diffusion barriers leads to a decrease in the concentration of cobalt atoms in the semiconductor surface layers. In diodes with the Co/Al2O3/GaAs contact, circularly polarized radiation is detected, which is caused by the injection of spin-polarized holes from the ferromagnetic contact into the semiconductor.

The effect of neutron radiation on the luminescence of InGaAs/GaAs heterostructures with quantum wells and quantum dots is studied. It is found that neutron radiation results both in the formation of defects and in the radiation-induced annealing of growth-related defects. Quantum dots are more stable to neutron radiation in comparison with quantum wells. It is shown that the layer of InGaAs/GaAs quantum dots located near the surface is less sensitive to irradiation with neutrons compared with a similar layer located in the bulk. In the first case, one can observe an increase in the photoluminescence and electroluminescence intensities after irradiation with neutrons, which is related to the effects of radiation-induced annealing. The pronounced effect of elastic strains in the InGaAs/GaAs quantum wells on the extent of quenching of the photoluminescence intensity upon irradiation with neutrons is revealed. In heterostructures with quantum wells, the effect of radiation-induced annealing manifests itself in a shift of the photoluminescence peak to longer wavelengths as a result of a decrease in elastic strains upon irradiation with neutrons. Doping of the GaAs buffer layer with silicon also reduces the value of this spectral shift.

Circularly polarized electroluminescence from GaMnAs/n++GaAs/n-GaAs/InGaAs/p-GaAs heterostructures is studied. A hysteresis-like magnetic field dependence of the degree of circular polarization can be attributed to the injection of spin-polarized electrons from the magnetized GaMnAs layer. This effect is observed in the temperature range 10–90 K.

The possibility of the epitaxial growth of ferromagnetic manganese gallide (Mn3Ga5) layers on a the GaAs(100) surface was demonstrated. The ferromagnetic properties of epitaxial Mn3Ga5 at room temperature were evaluated from measurements of the anomalous Hall effect. A diode structure based on the Mn3Ga5/GaAs contact was formed, and the low-temperature electroluminescence of this diode was measured. The possibility of electroluminescence and the high crystal quality of the structures under study showed promises of their application in light-emitting diodes with spin injection.

The temperature dependence of the circular polarization degree of the electroluminescence from light-emitting diodes based on InGaAs/GaAs-quantum-well (QW) heterostructures with a closely located ferromagnetic Mn δ layer is investigated. It is found that the Mn δ layer ferromagnetically affects holes in the QW. This effect is characterized by spin polarization of the holes and the appearance of circularly polarized emission components under electroluminescence conditions. It is demonstrated that the ferromagnetic properties of a δ layer can be studied by analyzing the QW luminescence. The Curie temperatures of the ferromagnetic system are determined using the results of investigations.

A diode structure with a p-n junction and an InGaAs/GaAs quantum well in the space-charge region and a ferromagnetic GaMnSb layer as the p-type semiconductor has been fabricated and studied. The possibility of obtaining high-efficiency electroluminescence (EL) from the structure was demonstrated. It was found that the EL efficiency depends on the growth parameters of the ferromagnetic GaMnSb layer, i.e., the Mn content and layer thickness. The possible mechanisms of EL from the diodes under study were considered. Circularly polarized EL was obtained from the structures. It was shown that the degree of polarization (0.012 in a magnetic field of 0.37 T) remains nearly invariable in the temperature range 10–50 K and the circular polarization of the emitted light is due to the injection of spin-polarized holes into the quantum well from the ferromagnetic GaMnSb layer.

Light-emitting diode structures with an InGaAs/GaAs quantum well and a ferromagnetic GaMnSb layer as a p-type semiconductor have been manufactured and investigated. A magnetic-field-induced circular polarization of electroluminescence in these structures has been obtained, the degree of which (0.012 at 0.37 T) is almost constant in the temperature interval of 10–50 K. Circular polarization is determined by the injection of spin-polarized holes from the ferromagnetic GaMnSb layer.

A self-organized InAs/GaAs quantum dot (QD) array is doped with Mn. The effect of the Mn concentration on the morphology and QD luminescence properties is investigated. It is found that Mn deltadoping of the GaAs buffer layer before QD growth with a layer concentration of 1014 cm−2 leads to the formation of an array of large QDs with variable composition In x Ga1 − x As. The effect is explained within a model of In and Ga atom interdiffusion.

A p-i-n light-emitting diode (LED) structure with an InGaAs/GaAs quantum well and a ferromagnetic GaMnAs layer as p-type semiconductor has been manufactured and investigated. An external magnetic field induces a decrease (up to ∼5% in a magnetic field of 3600 Oe at T = 10 K) in the GaMnAs layer resistance. In the voltage source regime, a change in this resistance leads to an increase in the intensity of electroluminescence of the given LED structure. This effect is due to ferromagnetism of the GaMnAs layer and vanishes at temperatures above the Curie point of this layer.

Phase equilibria in the Li,K‖Cl,MoO4 ternary mutual system were studied by differential thermal analysis (DTA). The characteristics of the following three ternary eutectics were determined: E 1: 348°C, 41 mol % KCl, 7.75 mol % Li2MoO4, and 51.25 mol % LiCl; E 2: 475°C, 44 mol % KCl, 17.25 mol % Li2MoO4, and 38.75 mol % LiCl; and E 2: 477°C, 35 mol % KCl, 47 mol % Li2MoO4, and 18 mol % LiCl.

GaAs structures with implanted Mn and, additionally, with Mg for increasing the hole concentration in the implanted Mn layer are synthesized and investigated. SQUID magnetometer measurements revealed the existence of ferromagnetism in the temperature range 4.2 K ≤ T < 400 K, which is associated with the formation of the Ga1−x Mn x As solid solution and MnAs and Ga1−y Mn y clusters in the sample as a result of rapid high-temperature annealing. At temperatures from 4.2 to approximately 200 K, the anomalous Hall effect associated with additional magnetization of the sample is observed. As the temperature increases from 4.2 K, the colossal negative magnetoresistance is transformed into a positive magnetoresistance at T ≈ 35 K.

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 MnyGa1 − y clusters as a result of high-temperature annealing, in addition to the formation of the Ga1 − xMnxAs 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.

The dependence of magnetic properties of GaAs:Mn and MnAs epitaxial films grown on GaAs (001) by laser ablation of Mn and undoped GaAs in a hydrogen atmosphere under the growth conditions has been studied by magnetic force microscopy (MFM). Magnetic probe calibration for quantitative MFM measurements was performed by scanning across the slit of the magnetic-head of a tape recorder through which controlled direct current was passed. The dipole approximation was used to describe the magnetic properties of the MFM probe. Nonuniformity of the magnetization of GaAs:Mn films related to the formation of MnAs nanoinclusions, which are ferromagnetic at 300 K, has been observed. The typical scales of the spatial nonuniformity of the magnetization of GaAs:Mn films were varied from 270 to 550 nm depending on the film-growth conditions. The MnAs phase was identified by MFM measurements at an elevated temperature (up to 80°N).