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The prognostic models assessing the risk of prehypertension in coming 1-2-year period for 30-60-year-old subjects were developed with the help of computer recognition technology using 6 recognition methods. These models are based on the content of molecular markers in blood serum and the risk factors for the development of prehypertension in men and women who had "optimal" BP for last 3 years and in patients with newly diagnosed prehypertension. The models were compared for their prediction power. The most effective model was obtained with gradient boosting method based on the content of molecular markers. It is characterized with a high predictive power (ROC AUC=0.76), specificity (96.4%), and overall accuracy (86.6%) accompanied with close relationship between prognosis and actual symptoms of prehypertension (p=0.001).

Pd–oxide–InP (MOS) structures are fabricated, and their physical and photoelectric properties in a hydrogen atmosphere are investigated. It is established that a decrease in photovoltage of the structure and a large increase in photocurrent in the circuit are observed under the pulsed effect of hydrogen on the structure with a palladium layer illuminated by a light-emitting diode (LED of the wavelength λ = 0.9 μm). The kinetics and mechanism of the variation in the photovoltage and photocurrent are considered. It is assumed that the photovoltage decreases because of the ionization of hydrogen atoms in the Pd layer, and the photocurrent increases due to the thermionic emission of nonequilibrium electrons from the Pd layer into the semiconductor. On the basis of results of the investigations, the sensitive element for an optoelectronic hydrogen sensor is developed.

The results of a study aimed at the development of high-efficiency photodiodes for the spectral range 1.5–3.8 μm with various photosensitive-area diameters in the range 0.1–2.0 mm are reported. Epitaxial techniques for the growth of InAs/InAsSbP photodiode heterostructures are developed. The distinctive features of the diodes are their high monochromatic current sensitivity Sλ of up to 1.6 A/W at the peak of the spectrum, λ = 3.0–3.4 μm, and the detectivity of the photodiodes, estimated by the experimentally measured noise level and the monochromatic current sensitivity, reaching at the spectrum peak a value of D* (λmax, 1000, 1) = (0.6–12) × 1010 cm Hz1/2 W–1 at T = 300 K. The bulk component of the reverse dark current in the photodiodes under study is constituted by two components: diffusion- and tunneling-related, with a low density of reverse dark currents j = (0.3–6) × 10–1 A/cm2 attained at a bias of U =–(0.2–0.4) V. The photodiodes are characterized by the product R0A = 0.4–3.2 Ω cm2. With the diameter of the photosensitive-area increased within the range 0.1–2.0 mm, the specific detectivity of a photodiode increases by nearly a factor of 2, which is due to the weaker effect of surface leakage currents with its increasing diameter. The response time of diodes of this kind varies within the range 1–300 ns, which enables their use in open-space optical communication systems in the atmospheric-transparency window. Photodiodes with a large sensitive area (up to 2.0 mm), high specific detectivity, and high photosensitivity can be used to detect absorption bands and record the concentrations of such substances as methane, ether, N2O, and phthorothanum.

The spectral characteristics of light emitting diodes based on a InAs/InAsSb/InAsSbP heterostructure, which emit in a wavelength range of 3.5–4.5 µm, are investigated experimentally. It is shown that the temperature shift of the maximum emission wavelength of a light emitting diode in the temperature range 80–313 K is 1.8 nm/K. The temperature dependence of the band gap of the InAs0.88Sb0.12 active layer is described by the Varshni formula with the characteristic parameters: Eg0 = 0.326 eV, a = 2.917 × 10–4 eV/K, and s = 168.83 K. The results of our measurements of the concentrations of carbon dioxide (CO2) using the studied light emitting diodes show the possibility of the reliable detection of CO2 in the concentration range 300–100000 ppm.

The neuroprotective and nootropic activities of the amide form (AF) of the HLDF-6 peptide (TGENHR-NH2) were studied in transgenic mice of the B6C3-Tg(APPswe,PSEN1de9)85Dbo (Tg+) line (the animal model of familial Alzheimer’s disease (AD)). The study was performed in 4 mouse groups: group 1 (study group): Tg+ mice intranasally injected with the peptide at a dose of 250 μg/kg; group 2 (active control): Tg+ mice intranasally injected with normal saline; group 3 (control 1): Tg- mice; and group 4 (control 2): C57Bl/6 mice. The cognitive functions were evaluated using three tests: the novel object recognition test, the conditioned passive avoidance task, and the Morris water maze. The results testify to the fact that the pharmaceutical substance (PhS) based on the AF of HLDF-6 peptide at a dose of 250 μg/kg administered intranasally efficiently restores the disturbed cognitive functions in transgenic mice. These results are fully consistent with the data obtained in animal models of Alzheimer’s disease induced by the injection of the beta-amyloid (βA) fragment 25-35 into the giant-cell nucleus basalis of Meynert or by co-injection of the βA fragment 25-35 and ibotenic acid into the hippocampus, and the model of ischemia stroke (chronic bilateral occlusion of carotids, 2VO). According to the overall results, PhS based on AF HLDF-6 was chosen as an object for further investigation; the dose of 250 μg/kg was used as an effective therapeutic dose. Intranasal administration was the route for delivery.

High-power light-emitting diodes (LEDs) with mesa diameters of 100, 200, and 300 μm are developed on the basis of InGaAsP/InP heterostructures. The mesas are close in shape to a truncated cone with a generatrix inclination angle of ∼45° in the vicinity of the active region of the LED, with a ring etched around the mesa serving as a reflector. The emission spectra and directivity patterns of these LEDs are studied in a wide range of current densities and it is shown that radiative recombination is dominant to a current density of ∼5000 A/cm2, which makes these structures promising for the development of high-power LEDs. An emission power of ∼14 mW is obtained in the continuous-wave mode (I = 0.2 A, λ = 1.1 μm), and that of 77 mW, in the pulsed mode (I = 2 A, λ = 1.1 μm), which corresponds to external quantum efficiencies of 6.2 and 3.4%, respectively.

The effects of serotonin and glutamate on DNA spatial fluorescent pattern after preliminary application of nifedipine and verapamil (inhibitors of L-type of potential-regulated Ca2+ channels) or caffeine (ryanodine receptors agonist) or BAPTA AM (membrane-permeable Ca2+ buffer) were in vivo studied in L-RPl1 neurons in isolated snail CNS preparation stained with SYTO16 AM. It was found out that preliminary applied BAPTA AM, caffeine, nifedipine or verapamil suppressed the neurotransmitter-induced changes in the number and size of spots in the neuronal nucleus of edible snail. At the same time by 30–120 min after an application of neurotransmitters in the presence of nifedipine, verapamil or BAPTA AM but not caffeine a pronounced increase in the number of large spots is produced, that probably reflects an activation of DNA compactization and chromatin condensation for this period. Obtained data suggest the presence of two consequent phases of DNA transformation evoked by neurotransmitters: (1) — extracellular Ca2+ dependent phase of chromatin decondensation and DNA decompactization (duration: about 1–2 h) and (2) subsequent (in 30 min after application of transmitters) extracellular Ca2+ independent caffeine-susceptible phase within which DNA compactization, chromatin condensation and the restoration of the initial DNA state occur.

Lasers operating on whispering gallery modes (WGMs) and emitting in the mid-IR wavelength range (2.2–2.4 µm) have been created on the basis of coupled semiconductor disk cavities with half-ring contacts. It is established that a separate connection of half-ring contacts of the WGM laser corresponds to a multimode character of radiation, while the connection of all (four) contacts leads to lasing in a single-mode regime. Possible mechanisms of mode synchronization in the proposed WGM lasers are discussed.

Pd-anodic oxide-InP metal-oxide-semiconductor (MOS) structures are fabricated to develop a hydrogen sensor capable of effectively operating at room temperature. The conduction mechanisms of the structures at 100–300 K are studied. It is found that the oxide behaves as ohmic resistance and the rectifying properties of the structures are determined by the potential barrier at the oxide-InP interface with the thermal-tunneling charge transport mechanism. The structures greatly change their characteristics in the presence of hydrogen in the ambient medium.

The temperature dependence of the threshold current and emission spectra of disk-shaped quantum-well whispering-gallery mode (WGM) lasers is studied in the temperature range of 80–463 K in which the laser emission wavelength increases from 2 to 2.5 μm. It is shown that lasing is observed up to 190°C. Radiative recombination is dominant up to a temperature of 300 K, and nonradiative Auger recombination, in which a recombining electron gives energy to another electron, is so at higher temperatures. The spin-orbit split-off valence subband is not involved in recombination processes, which is attributed to mechanical compression of the quantum-well material.

InAs/InAs0.88Sb0.12/InAs0.50Sb0.20P0.30 heterostructure photodiodes operating at room temperature in the spectral range 1–4.8 μm are developed. It is shown that the formation of a curvilinear reflecting surface constituted by a number of hemispheres on the rearside of the photodiode chip leads to an increase in the quantum sensitivity of the photodiodes by a factor of 1.5–1.7 at wavelengths in the range 2.2–4.8 μm. At an exposed photodiode area of 0.9 mm2 and a p-n junction area of 0.15 mm2, a zero-bias differential resistance of 30 Ω and a quantum sensitivity of 0.24 electron/photon at a wavelength of 3 μm are obtained. The operation of a photodiode with re-reflection of the photon flux in the crystal due to reflection from the curvilinear surface of the rearside of the photodiode chip is theoretically analyzed. The possibility of effective conversion of the re-reflected flux of photons into a photocurrent, with a simultaneous decrease in the p-n junction area, is demonstrated. An increase in the quantum sensitivity in the short-wavelength spectral range 1–2.2 μm by 35% relative to the calculated data is observed, which is probably due to impact ionization in the narrow-gap active region.

A new method for the passivation of IR (1.5 – 5.0 μm) photo diode surfaces is offered using a mix of heavy fullerenes (HFull-mix): С76 + С78 + С84 + С90 + … Principal operational characteristics of the diodes are researched. It is shown that with such passivation the dark current of the photo diodes decreases 14 %. The Peltier effect on heterojunction “semiconductor A3B5/HFull-mix” is found.

It is shown, using the example of InAs/InAsSb/InAsSbP heterostructures, that the formation of a curvilinear reflecting surface consisting of hemispherical etch pits on the rear side of a photodiode chip leads to an increase in the quantum efficiency of photodiodes by a factor of 1.5–1.7 in the entire mid-IR wave-length interval studied (λ = 3–5 μm). For the obtained photodiodes with a cutoff wavelength of 4.8 μm, a photosensitive area of 0.1 mm2, and a chip area of 0.9 mm2, a monochromatic responsivity at λ = 4.0 μm reached 0.6 A/W, while a dark current at a reverse bias voltage of 0.2 V was within 4–6 A/cm2.

Nonlinear optical properties (particularly optical limiting) are determined for solutions of heavy fullerenes C76 + C78 + C84 + C90 + …, in the near-ultraviolet region (λ ≈ 280 ± 7 nm). It is shown that no optical limiting is observed in solutions of light fullerenes (C60 and C70), but found in solutions of water-soluble fullerenol-d (a mixture of oxypolyalcohols of fullerene C60-C60(OH)n1On2, with their sodium salts) based on light fullerenes.

A new pathway for passivation of the surface of infrared photodiodes and light-emitting diodes operating at room temperature in the spectral range of 2–5 μm by individual fullerene C70 is proposed and its characteristics are studied. It is determined that during the passivation of photodiodes, dark current falls by 40% and resistance at zero bias increases by 24%; for light-emitting diodes, leaks fall by ∼20%, and resistance at zero bias increases by 45% and the intensity of emission of light-emitting diodes increases by ∼18% after the application of fullerene C70.

A new method for the passivation of the surface of infrared photodiodes operating at room temperature, spectral range 1.5–5.0 μm, by a mixture of higher fullerenes (h-f-mix) C76 + C78 + C84 + C90 + … was suggested. The main service characteristics of photodiodes were studied. The passivation of photodiodes decreased their dark current by 14%. The Peltier effect was observed for the A3B5 semiconductor/h-f-mix heterojunction.

The effect of passivation with the solution of sodium sulfide (Na2S) in isopropyl alcohol on the room-temperature performance of the GaInAsSb/GaAlAsSb and InAs/InAsSbP photodiodes is investigated. After such a treatment the dark current density of the GaInAsSb/GaAlAsSb photodiodes at a reverse bias of 0.1 V is reduced from 5.5 × 10−2 to 2.1 × 10−3 A/cm2 and a zero-bias resistance-area product (R 0 A) is improved from 1.0 to 25.6 Ω cm2. For the InAs/InAsSbP photodiodes, the dark current density at U = −0.1 V is decreased from 1.34 to 8.1 × 10−1 A/cm2, while the R 0 A value increases from 4.4 × 10−2 to 7.3 × 10−2 Ω cm2. The method offers long-term stability of the photodiode performance.

Spectral and spatial distributions of the emission of whispering-gallery-mode (WGM) lasers with a half-disk cavity have been studied. Up to 13 broad lobes with different intensities, subdivided into order-of-magnitude narrower lobes, are distinguished in the spatial distribution. The emission spectrum is nearly single-mode. A mathematical model of the electromagnetic field distribution in a WGM laser is suggested, and the radiation pattern of the laser is calculated. It is shown that each lobe corresponds to its own stable radial spatial mode. The highest emission intensity is provided not by the peripheral mode itself, but by the next-closest mode, which presumably exhibits the lowest optical loss. The predominance of a single spatial mode results in a nearly single-mode emission spectrum being observed.

We have observed the interference of rays in a whispering gallery mode (WGM) semiconductor diode laser with a half-disk cavity. The interference leads to the formation of about 20 lobes in the radiation directivity pattern in the far field zone. Each of these lobes consists of even narrower components. It is established that the number of narrow lobes is determined by the coherent counterphase rays originating from peripheral points of the half-disk cavity mirror. The wide lobes are related to adjacent coherent radiation sources, the presence of which is confirmed by the near field pattern.

Frequency tuning in a whispering gallery mode (WGM) semiconductor laser (λ = 2.35 µm) with a sector (half-disk) cavity has been studied. Pumping by current pulses with a duration of up to 1.2 µs is accompanied by smooth tuning of the main WGM toward longer wavelengths by 30 A at room temperature, which is 1.4 times the intermode distance.

For disc lasers based on the InAs/InAsSbP heterostructure with a generation wavelength of 3.03–3.06 μm, the internal quantum yield of luminescence and rates of radiative and nonradiative recombination in a temperature range of 85–120 K are determined. It is established that as the temperature increases, the relative contribution of the rate of nonradiative recombination to the density of the threshold current increases from 89.9 to 92.8%. It is shown that the most probable mechanisms of nonradiative transitions in the InAs/InAsSbP disc heterolasers can be the CHCC and CHSH Auger processes with involvement of phonons. Coefficients of total losses for two experimentally observed generation bands are determined, and the maximum level of the internal optical losses is estimated. The figure of merit of the resonator of the InAs/InAsSbP disc heterolaser is ∼104.

IR semiconductor WGM lasers operating in the continuous-wave (CW) mode at a wavelength of 3.04 μm have been fabricated by metal-organic vapor-phase epitaxy on the basis of InAs/InAsSbP heterostructures. Their emission spectra were studied in the temperature range from 77 to 125 K. The lasers operating in the CW mode have a threshold current of 25 mA at a temperature of 77 K. The WGM lasers also work in the pulsed mode up to 125 K. The dynamic range of operation for the disk lasers is substantially extended to currents exceeding the threshold current by a factor of 200.

A new method for simulating electroweak top-quark production processes is described along with its computer realization in the SingleTop event generator. Special attention is paid to the correct combination of events from two parts of the main t-channel production process: 2 → 2 with a b quark in the initial state and 2 → 3, where an additional b quark appears in the final state. Integration of these two contributions enables the generation of event samples including the first correction to the leading perturbation order, avoiding the double-counting problem and negative-weight events. The SingleTop generator is based on the complete set of the tree Feynman diagrams calculated by the CompHEP package.

It is demonstrated, using the example of light-emitting diodes (LEDs) based n-GaSb/n-GaIn-AsSb/p-GaAlAsSb heterostructures, that the formation of a curvilinear reflecting surface consisting of hemispherical etch pits on the rear side of an LED chip leads to an increase in the output radiation power by a factor of 1.9–2 in the entire wavelength interval studied (λ = 1.7–2.4 μm) as compared to the LED chip design with a continuous absorbing ohmic contact. This increase in the LED efficiency is related to a change in the directions of reflected light fluxes upon reflection from the hemispherical etch pits.

The temperature dependence of the threshold current density and emission spectra of disk-shaped quantum-confinement lasers operating on whispering-gallery modes has been studied in the 23–180°C interval. As the temperature is increased in this interval, the radiation wavelengths grows from 2.24 to 2.42 μm, stable lasing is observed up to 177°C, and the threshold current exhibits exponential growth in proportion to exp(T/T0) with T0 = 70 K.

A new approach is presented which has wide-ranging application for the modeling and understanding of both open multi-phase crystallization from the melt while the temperature is decreasing. and isothermal crystallization from Solution while solvent is evaporating. The results are widely applicable. Examples are given which relate to laboratory situations such as the liquid-phase epitaxial growth of complex III-V alloys and also to crystallization processes in oceans or sea water. (C) 2002 Elsevier Science B.V. All rights reserved.

The effects of antibodies to a total fraction of s100 proteins and protein s100b on the activity of defensive behavior command neurons LPl1 and RPl1 were studied in common snails, using non-sensitized animals and animals which had acquired nociceptive sensitization. In non-sensitized snails, application of antibodies against s100 or s100b (0.1 mg/ml) induced membrane depolarization, increased membrane permeability, and suppressed slow excitatory postsynaptic potentials in the responses of neurons to sensory stimulation. Acquisition of sensitization in snails in the presence of antibodies to s100 or s100b (0.1 mg/ml) led to significantly less marked facilitation of synaptic transmission and smaller increases in neuron membrane excitability than in cells of control sensitized animals. The difference in synaptic facilitation in the neurons of control sensitized snails and neurons in sensitized snails given antibody was comparable with the magnitude of synaptic depression due to antibody in non-sensitized animals. At a dose of 0.01 mg/ml, antibody had no effect on these measures of neuron activity. It is suggested that s100 proteins, particularly s100b, are involved in the mechanisms regulating excitability, the membrane potential, and synaptic transmission in command neurons in untrained snails, as well as in the mechanism of plasticity of the electrogenic membranes of nerve cells during the acquisition of nociceptive sensitization.

Photodiodes with a photosensitive area diameter of 0.3 mm operating at room temperature in a middle-IR (2.5–4.9 μm) wavelength range have been created based on InAs/InAs0.94Sb0.06/InAsSbP/InAs0.88Sb0.12/InAsSbP/InAs heterostructures grown by liquid phase epitaxy. Distinguishing features of the proposed photodiodes are a high monochromatic responsivity, which reaches a maximum of 0.6–0.8 A/W at λmax = 4.0–4.6 μm, and a low dark current density of (1.3–7.5) × 10−2 A/cm2 at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 700–800 Ω. The detection ability of photodiodes in the spectral interval of maximum sensitivity reaches (5–8) × 108 cm Hz1/2 W−1.

Whispering-gallery-mode (WGM) lasers (emission wavelength λ = 2.1–2.4 μm) with coupled disk cavities connected by a bridge are developed on the basis of a GaInAsSb/GaAlAsSb quantum-well nano-heterostructure and their emission spectra and optical far-field patterns are studied. Almost single-mode lasing in one spatial mode is observed in a wide range of supply currents. The emission wavelength grows with increasing current due to heating of the laser, and this phenomenon can be used in diode-laser spectroscopy. An assumption is made that the flux of generated emission can pass in lasers of this kind from one cavity to the other and back along the cavity-connecting bridge. It is found that strong narrowing of the laser emission pattern occurs with increasing current near the plane separating the coupled cavities.

A mid-infrared light-emitting diode (LED) operating at 3.6 µm with a pulsed output power as high as 2 mW at room temperature is reported. The device is based on a double heterostructure of InAs0.42Sb0.18P0.40/ GaxIn1−xAs1−ySby/InAs0.42Sb0.18P0.40 grown by liquid phase epitaxy. The active region composition was adjusted using different Ga content (x = 0.05–0.17) over which range the band gap is approximately constant. The electrical and optical operating characteristics are reported. The emission spectra measured with and without 100% formaldehyde have also been measured using a short-path optical cell to demonstrate the potential of these LEDs for use in solid state formaldehyde gas sensors. (Some figures in this article are in colour only in the electronic version; see www.iop.org)

Electroluminescence has been observed at 3.3 µm from InAs quantum well LEDs grown from the liquid phase for the first time. A special rapid slider liquid phase epitaxial growth technique was used to produce the wells within the active region of an InAsSbP homojunction p-i-n LED. The light emission was attributed to type II recombination between confined electron and hole states at the InAsSbP/ InAs interfaces of the InAs quantum well. Intense electroluminescence emission was observed at low temperatures from a multi-interface LED which contained three InAs quantum wells in the i-region of the LED structure with emission peaking at 3.68 µm at 250 K.

Previous publications concerned with the development and investigation of InAsSb/InAsSbP double heterostructure lasers emitting at 3–4 µm fabricated by liquid phase epitaxy are reviewed. In pulsed mode, the maximum operating temperature of the lasers is 203 K, the characteristic temperature is 35 K, and differential quantum efficiency is 20±5% at 77K. Mesa-stripe lasers with a 10-to 30-µm stripe width and a 200-to 500-µm cavity length can operate in CW mode up to 110 K. The total optical output power of more than 10 mW at λ=3.6 µm is obtained at T=82 K in CW mode. The output power per mode does not exceed 2 mW/facet. A single-mode lasing is achieved in the temperature range of 12–90 K.

A new type of mid-infrared LED module (LEDM) operating at 3.8 mu m is reported. The device was produced using liquid phase epitaxy (LPE) and consists of a series array of four individual LED chips. Electro-optic characteristics of the devices were measured and are reported here. The output power from the module was measured to be as high as 8 mW at room temperature under pulsed drive conditions. Compared with previous results our LED and LEDM devices represent a considerable improvement in output power at 3.8 mu m. The reasons for this improvement are related to the purification techniques used in the LPE growth procedure and the de-tuning of the CHSH Auger resonance in the InAs0.95Sb0.05 alloy which forms the active region. The peak in the electroluminescence emission spectrum was found to be co-incident with the absorption band of H2S gas and as such we were able to demonstrate substantial optical absorption which clearly shows the potential application of such devices in infrared gas sensor instrumentation.

A report is presented on the development of a single-mode laser based on the InAsSb/InAsSbP double heterostructure and operating at wavelengths of 3.2–3.3 µm in a temperature range of 12–90 K. The single-mode regime is assumed to be realized due to a smooth optical waveguide formed across the laser cavity in which the radiation flux oscillates and maintains its oscillations and intensity. An analysis is made of the effect of the current-induced shifts of the lasing frequency and the peak of the gain spectrum on the probability of single-mode lasing. Experiments were made on the scanning of OCS, NH3, CH3Cl, and H2O gas media with radiation of the given laser in the frequency range with a record width of 10 cm−1 (104 A).

We report on the direct observation of an increase in the wavelength of output radiation during the pumping current pulse in a whispering gallery mode (WGM) semiconductor diode laser (2.35 μm) with a sector (half-disk) cavity. During the current pulse with a duration of up to 1.5 μs, the main WGM wavelength smoothly increases by 30 A at room temperature.

Powerful (light emitting diodes) LEDs which exhibit more than 3.5 mW of output power at room temperature have been fabricated by liquid phase epitaxy (LPE) and characterized. These LEDs are well matched to the CH4 absorption spectrum and confirm the potential of the devices as a key component for use in an infrared CH4 gas sensor. We report on the efficient interface electroluminescence in our LEDs across the InAs/InAsSbP heterojunction consistent with type II emission. This directly suppresses the Auger recombination and enables these sources to emit maximum powers in excess of 3 mW at room temperature. Furthermore, the use of Yb rare earth ion gettering in these devices was found to be effective in increasing the LED output power. We attribute this to a reduction in the residual carrier concentration arising from the removal of unintentional donors and point defects in the InAs active region material. The ring contact geometry was also found to be superior when compared to the dot contacts in our structures. The LEDs demonstrated in this work are sufficiently powerful to be used in a practical methane gas sensor. (Some figures in this article appear in colour in the electronic version; see www.iop.org)

The current dependence of the output frequency of InAsSb/InAsSbP diode lasers at wavelengths near 3.6 µm is studied. It is found that in these lasers the number of lasing modes can be reduced without introducing crystallographic defects. It is shown that the photon momentum aids in suppressing the spectral modes closest to the dominant mode. Two-mode laser spectroscopy is done over an interval of 2 cm−1 for two gases, N2O and CH3Cl.

A reduction in the emission wavelength in the preferred mode of InAsSbP/InAsSb/InAsSbP heterostructure lasers by 50A is observed when the current is raised from 1.8 to 5 times the threshold with dc and pulsed power. A comparison of the spectral and spatial distributions of the output as functions of current shows that this short-wavelength tuning is caused by a change in the distribution of the nonequilibrium charge carrier concentration over the strip width as the current is varied. This effect is modeled mathematically, taking into account the increase in the injection density and the drop in the output intensity from the middle to the sides of the waveguide. The results of the model calculation are in good agreement with experiment.

Anomalously narrow, single-lobe and double-lobe beam directivity patterns in the plane of the p-n junction have been observed in lasers constructed from InAsSb/InAsSbP heterojunctions emitting at a wavelength of approximately 3.3 µm. Theoretical near-field and far-field radiation distributions for the laser emission of two beams oscillating across the stripe are obtained on the basis of new concepts of the lasing processes. The single-lobe directivity pattern is obtained for the emission of in-phase beams, and the double lobe is obtained for antiphase beams. Correspondence of the theory with experiment is established.

The electrical properties of epitaxial InAs and solid solutions based on it (InGaAsSb, InAsSbP, InAsGa, InAsP) have been investigated. It is shown that intentionally undoped crystals have n-type conductivity, which is determined by shallow donor impurities (E 1=0.002–0.003 eV) and structural defects (E 2=0.02–0.03 eV and E 3=0.09–0.10 eV). It is shown that growth of epitaxial InAs using the neutral solvent Pb and also rare-earth elements makes it possible to reduce the electron density by almost an order of magnitude (to levels as low as 3×1015 cm−3) due to due to a decrease in the density of structural defects.

Light-emitting diodes (LED’s) operating in the spectral range 1.9–2.1 µm have been fabricated by liquid-phase epitaxy on the basis of AlGaAsSb/GaInAsSb double heterostructures with a high Al (64%) content in the wide-gap regions. The design of the LED makes it possible to locate the active region near the heat-removal elements of the housing, and pass the light through the GaSb substrate, which is completely unshielded by the contact. The LED’s are investigated in the quasi-continuous (CW) regime and pulsed regime at room temperature. The optical power of the LED’s possesses a linear current dependence over a wide range of currents. A CW optical power as high as 4.6 mW and a peak optical power of 190 mW in the pulsed regime were achieved at room temperature. It is shown that the transition from linear to sublinear current dependence of the optical power is governed by Auger recombination in the pulsed regime at pulse durations as low as 5 µs.

A study has been made of wavelength tuning in double heterostructure InAsSb/InAsSbP-based diode lasers. A simple mathematical model, which takes into account the spatially homogeneous injection and the dependence of the dielectric constant on the charge carrier density, is discussed. The wavelength can be increased or decreased, depending on the pump current and diode structure parameters, as is observed experimentally. The process of wavelength tuning proceeds with virtually zero delay time since it is determined by the photon lifetime in the cavity and in part by the lifetime of nonequilibrium charge carriers.

Disk-shaped cavities in the form of cylinders with diameters of 200, 100, and 50 μm and a mesa height of up to 30 m with the vertical part of the side surface reaching 10 m have been created for the first time for whispering gallery mode (WGM) semiconductor lasers based on InAs/InAsSb0.11P0.24 heterostructures. The cavities were formed by etching in a specially selected HBr-H2Cr2O7-H3PO4 mixture, which ensured an increase in the length of the vertical part of the side surface at a decrease in the surface roughness. These improvements increased the stability of optical modes in the disk cavity of the WGM laser and ensured generation with a wavelength of λ ≈ 3 μm in a continuous regime at 77 K.