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We have examined the two-state operation process of the high-power edge-emitting lasers based on AlGaAs/InGaAs/GaAs heterostructure with a thick (90Å) quantum well in the active region. It has been demonstrated that the laser emission spectrum can be switched between spectral lines corresponding to different optical transitions between the quantum states in the active region. The switching process is governed either by pump current or by temperature. The dynamic characteristics of the switching laser pumped with 100 ns current pulses have been investigated and explained. It has been shown that the current density dependence of internal optical loss can cause the currentinitiated switching. The temperature impact is much more important and consists in the charge carrier redistribution in the quantum well. The registered optical power near the switching point was near 2W in continuous wave and 15W in pulse mode of operation. [ABSTRACT FROM AUTHOR]

The room-temperature generation of multiperiod quantum-cascade lasers (QCL) at a wavelength of 5.8 μm in the pulsed mode is demonstrated. The heterostructure of a quantum-cascade laser based on a heterojunction of InGaAs/InAlAs alloys is grown by molecular-beam epitaxy and incorporates 60 identical cascades. The threshold current density of the stripe laser 1.4 mm long and 22 μm wide is ~4.8 kA/cm at a temperature of 303 K. The maximum power of the optical-radiation output from one QCL face, recorded by a detector, is 88 mW. The actual optical-power output from one QCL face is no less than 150 mW. The results obtained and possible ways of optimizing the structure of the developed quantum-cascade lasers are discussed. [ABSTRACT FROM AUTHOR]

Nanostructured aluminum-nitride films are formed by reactive ion-plasma sputtering onto GaAs substrates with different orientations. The properties of the films are studied via structural analysis, atomic force microscopy, and infrared and visible-ultraviolet spectroscopy. The aluminum-nitride films can have a refractive index in the range of 1.6-4.0 at a wavelength of ~250 nm and an optical band gap of ~5 eV. It is shown that the morphology, surface composition, and optical characteristics of AlN/GaAs heterophase systems can be controlled using misoriented GaAs substrates. [ABSTRACT FROM AUTHOR]

Structural and spectroscopic methods are used to study the epitaxial layers of n-type AlGaAs solid solutions produced by the metal-organic chemical vapor deposition method. It is shown that, when AlGaAs solid solutions are doped with carbon to a level of (1.2-6.7) × 10 cm, the electron mobility is anomalously high for the given impurity concentration and twice exceeds the calculated value. It is assumed that the ordered arrangement of carbon in the metal sublattice of the solid solution leads to a change in the average distance between impurity ions, i.e., to an increase in the mean free path of the carriers and, consequently, in the carrier mobility. The observed effect has immediate practical importance in the search for various technological ways of increasing the operating speed of functional elements of modern optoelectronic devices. The effect of the anomalously high carrier mobility in the epitaxial layer of a heteropair opens up new opportunities for the development of new structures on the basis of AlGaAs compounds. [ABSTRACT FROM AUTHOR]

The effect of temperature delocalization in semiconductor lasers (emission wavelength λ = 1060 nm) based on symmetric and asymmetric separate-confinement heterostructures fabricated by metal-organic vapor-phase epitaxy (MOVPE) is studied. Experimental and calculated estimates show that the carrier concentration in the waveguide increases by an order of magnitude when the temperature of a semiconductor laser is raised by ∼100°C. It is found that an increase in the temperature of the active zone leads to enhancement of the temperature delocalization of both electrons and holes. It is shown that the delocalization of holes begins at higher temperatures, compared with that of electrons. It is demonstrated experimentally that the onset of temperature delocalization depends on the threshold carrier concentration in the active region of a laser at room temperature. It is found that raising the energy depth of the active region by choosing the waveguide material makes it possible to fully suppress the temperature-delocalization process up to 175°C. [ABSTRACT FROM AUTHOR]

Two types of laser heterostructures, i.e., those without internal mechanical stress compensation, with AlGaAs-alloy emitter and waveguide layers (type 1), and laser heterostructures with stress compensation, with AlGaAsP emitter and waveguide layers (type 2) are grown by metal-organic chemical vapor deposition (MOCVD). Laser-diode bars 5 mm wide with a fill factor of 24%, emitting at a wavelength of 850 nm are fabricated. Their power parameters in the continuous-wave (cw) and pulsed lasing modes are studied. It is shown that type-2 laser diode bars exhibit better linearity of the light-current characteristics in the cw and pulsed lasing modes in comparison with laser diode bars based on the type-1 structure. [ABSTRACT FROM AUTHOR]

The study is concerned with MOCVD epitaxial heterostructures grown on the basis of AlGaInAsP quinary alloys in the region of alloy compositions isoperiodic to GaAs. By the X-ray diffraction technique and atomic force microscopy, it is shown that, on the surface of the heterostructures, there are nanometric objects capable of lining up along a certain direction. From calculations of the crystal lattice parameters with consideration for internal strains, it can be inferred that the new compound is a phase based on the AlGaInAsP alloy. [ABSTRACT FROM AUTHOR]

A new mechanism describing the rise in the contact resistance ρ of ohmic contacts to n- n- n-GaAs(GaP, GaN, InP) structures with increasing measurement temperature T, experimentally observed in the temperature range 100-400 K, is suggested on the basis of a theoretical analysis of the temperature dependence of ρ. Good agreement between the experimental and theoretical ρ( T) dependences is obtained and explained for a case where there is a high density of dislocations (on which metallic shunts are localized) in the near-contact region of the semiconductor. [ABSTRACT FROM AUTHOR]

Heterostructures with an active region containing a GaInAs quantum well located between GaAsP compensating layers were studied using photoluminescence spectroscopy. It was shown that an increase in the phosphorus content in compensating layers makes it possible to obtain unrelaxed heterostructures with wider GaInAs quantum wells. On the basis of photoluminescence studies, the parameters of such a composite active region were chosen with a view to attaining the longest lasing wavelength possible. Laser heterostructures with a composite active region consisting of a highly strained GaInAs quantum well located between GaAsP compensating layers were grown on GaAs substrates by metalloorganic chemical vapor deposition. Stripe mesa-structure laser diodes of 100-μm aperture emitting at 1220 nm were fabricated. The highest emission power of these laser diodes in the continuous-wave regime amounted to 2 W per output mirror. [ABSTRACT FROM AUTHOR]

InGaAs/GaAs/AlGaAs laser heterostructures are grown by MOCVD epitaxy on GaAs substrates. Mesastripe laser diodes with an aperture of 100 μm emitting at a wavelength of 1190 nm are fabricated. It is shown that, in these lasers, the active region is relaxed, which manifests itself in the spread of attainable maximal power for various lasers obtained from the same heterostructure. The maximal emission power in a CW mode of lasing for such lasers was 5.5 W per mirror. [ABSTRACT FROM AUTHOR]

The possibility of using the normal skin effect in dielectric waveguides for long-wavelength radiation is analyzed. A design of a waveguide integrated with a heterolaser is suggested, in which an undoped layer of GaAs is clad between heavily-doped n- and p-Al x Ga1 − x As alloy layers, reflecting radiation because of the normal skin effect. It is shown that an efficient waveguide can be formed using n-Al x Ga1 − x As layers with x < 0.45 and the electron concentration N > 5 × 1018 cm−3 and p-Al x Ga1 − x As layers of any composition with the hole concentration P ≥ 3 × 1019 cm−3. [ABSTRACT FROM AUTHOR]

Based on the results of model calculations and the data of photoluminescence measurements and transmission electron microscopy, the optimum composition (GaAs0.85P0.15) of compensating barriers for a structure with four highly strained Ga0.76In0.24As quantum wells (QWs) has been established that excludes the relaxation of elastic stresses in these QWs. Laser heterostructures with four such QWs separated by said compensating barriers have been grown by means of hydride metalorganic chemical vapor deposition. Laser diodes with short (∼100 μm) resonators based on these heterostructures operate at λ = 1060 nm with an output radiation power of 100 mW in the continuous regime. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Separate confinement AlInGaAs/InP multiwell laser heterostructures emitting in a wavelength range of 1.2-1.5 μm have been synthesized by metalorganic vapor-phase epitaxy. The threshold current of laser diodes with a strip width of 4.5 μm and a cavity length of 200 μm was as low as 10 mA. With a cavity length of 1.0 mm, the threshold current density was 500-650 A/cm². The laser diodes can operate in a continuous regime without forced cooling at an ambient temperature of up to 170°C. In a temperature range from 10 to 80°C, the characteristic temperature parameter TO reached up to 110 K. [ABSTRACT FROM AUTHOR]

Temperature dependences of the threshold characteristics of InGaAsP/InP quantum well (QW) lasers have been studied. The main contribution to the threshold current is made by the thresholdless Auger recombination. The observed power-law temperature dependence of the threshold current is explained by the predominance of the thresholdless Auger recombination in QWs over the threshold Auger process. [ABSTRACT FROM AUTHOR]

Liquid-phase epitaxy of InGaAsP solid solutions isoperiodic with (001)GaAs substrates was studied in the miscibility gap. At the initial stage of deposition (first 1-2 s), thin (up to 0.15 µm) planar layers of homogeneous InGaAsP solid solutions are formed. This is aided by pronounced supercooling of the melt (by 10-15°C) and the resulting high growth rates. In further stages, growth becomes slower and a natural nanoheterostructure starts to form owing to decomposition of the solid solution. The formation of a nanoheterostructure comprising domains of different compositions with different lattice constants is accompanied by the appearance of an undulating relief on the sample surface, with the undulation magnitude increasing as the layer grows. Under the technological conditions employed, the thickness of InGaAsP solid solution layers containing a nanoheterostructure is limited to 0.5 µm. [ABSTRACT FROM AUTHOR]

InGaAsP epitaxial layers, which are obtained in the instability region on InP (001) and GaAs (001) substrates, are investigated by photoluminescence and transmission-electronmicroscopy methods. The results are discussed on the basis of the theory of spinodal decomposition of solid solutions. It is established experimentally that in certain temperature and composition ranges the solid solutions InGaAsP are a system of charged, alternating (in mutually perpendicular directions [100] and [010]) domains of a solid solution with two different compositions and different lattice constants. The domain structure is very clearly defined at the surface of the epitaxial film and becomes blurred in the film near the substrate. The data obtained very likely show spinodal decomposition of the solid solutions InGaAsP in the test samples. [ABSTRACT FROM AUTHOR]

Semiconductor InGaAs/GaAs injection lasers emitting at λ = 1065 nm have been created with waveguides based on a single InGaAs quantum well. It is found that internal optical losses are determined by the width of an undoped region confined between the n and p type emitters. The room-temperature total output optical power in lasers with 100 μm aperture amounted up to about 2 W at a radiation beam divergence of 15° in the plane perpendicular to the p- n junction. [ABSTRACT FROM AUTHOR]

We have studied the protective properties of thin films of gallium selenide formed by the method of heterovalent substitution on the surface of GaAs substrates. The data of transmission (Hitachi H-800) and scanning (JEOL JSM-638 OLV) electron microscopy showed that GaAs substrates treated with selenium vapor produced a more pronounced orienting action on the subsequent deposition of GaAs as compared to the substrates covered with a natural oxide. The processing of a GaAs substrate in selenium vapor followed by the removal of the resulting Ga2Se3 layer increases the degree of smoothness of the substrate surface on the atomic level. [ABSTRACT FROM AUTHOR]

Two-photon absorption of 1.55 gm light in quantum-well InGaAs/InP laser heterostructures has been studied. The highest achieved nonlinear response was 0.78 nA/mW². The minimum detectable peak power of 60 µW allows for the effective use of waveguides of this type as detectors in optical autocorrelators for studying temporal characteristics of low-power signals. [ABSTRACT FROM AUTHOR]

Separately bounded InGaAsP/InP laser heterostructures with two stressed quantum wells emitting at a wavelength of 1.8 µm were obtained by metalorganic vapor-phase epitaxy. The laser diodes with a strip width of 100 µm provide for an output radiation power of 1.2 W in the continuous operation mode at a temperature of 20°C. A minimum threshold current density was 320 A/cm² and a differential quantum efficiency was η[sub d] = 28% for a Fabry-Perot resonator length of 1.4 mm. The internal optical losses in the laser heterostructure studied amounted to 5.6 cm[sup -1]. [ABSTRACT FROM AUTHOR]