The effect of an external resonator on the operation of a single-mode stripes laser bar based on an asymmetric InGaAs/AlGaAs/GaAs heterostructure is studied. It is shown that the external resonator increases the efficiency of optical coupling between bar stripes and to obtain laser generation in a high-order common mode with radiation pattern individual lobes about 1 deg.

The temporal behavior of an optical power at different moments of pulse in the far field is studied for a laser array $(\lambda=1060\ \text{nm})$ based on InGaAs/AlGaAs/GaAs. An array of narrow-stripe laser diodes with a straight ridge of $6.5-\mu\mathrm{m}$ width and a $13.5\ \mu\mathrm{m}$ -wide pitch without distributed feedback elements demonstrates that despite the strong optical coupling between adjacent array elements the lateral far fields only slightly differ from each other in width at half maximum (FWHM) (by $\pm 0.5^{\circ}$ ) at different moments of the pulse (130 ns/1 kHz) at a pump current amplitude of 5 A.

Pulsed radiative characteristics of high-power semiconductor lasers based on an asymmetric InGaAs/AlGaAs/GaAs heterostructure with an active region including two quantum wells and a gradient waveguide on the side of the p-emitter are studied. It is shown that the use of the proposed design allows efficient laser operation under pumping by 100-ns current pulses in the temperature range 25 – 90 °C. The lasers with a Fabry – Perot cavity 2900 μm long demonstrated peak powers of 62 W (injection current 123 A) and 43 W (122 A) at temperatures of 25 and 90 °C, respectively. It is found that at room temperature and currents of ∼50A, a decrease in the cavity length to 600 μm does not cause a decrease in the output power with respect to the power of lasers with a long (2900 μm) cavity. An increase in temperature to 90 °C at high injection currents leads to a sharp decrease in the radiative efficiency of lasers with a short (600 μm) cavity and to the change of their operation regime to the two-band lasing.

Thin aluminum nitride (AlN) films have been synthesized by reactive ion–plasma sputtering (RIPS) and their properties have been studied in view of using this method for obtaining protective coatings on output facets of high-power semiconductor laser cavities based on Al x Ga 1 − x As/GaAs heterostructures. Investigations by energy-dispersive X-ray spectroscopy and ellipsometry techniques showed that, at a residual pressure of ~10 –5 Torr, a layer of aluminum oxynitride is formed and the film–substrate heteroboundary may experience to oxidation. However, AlN films with thicknesses on the order of 100 nm grown in pure nitrogen at a residual pressure of ~10 –7 Torr were evidently free of oxygen and could reliably prevent its penetration to the region of heteroboundary.

The paper presents the results of the synthesis of thin aluminum nitride films by reactive ion-plasma sputtering and the study of their properties with the aim of using as the protective coatings for the high-power AlxGa1-xAs/GaAs semiconductor laser heterostructures. EDS studies and ellipsometry showed that at a residual pressure in the chamber of the order of ~10-5 Torr, a layer of aluminum oxynitride is formed in the films. In this case, the film-substrate heterointerface can undergo oxidation. However, AlN films with a thickness of the order of 100 nm grown in a pure nitrogen medium with a residual pressure of ~10-7 Torr apparently do not contain oxygen, and can reliably prevent its penetration into the heterointerface region. Potentially, they can serve as effective protection for oxidation sensitive heterostructures.

The concentration profiles of defects produced in structures upon the implantation of nitrogen ions into GaAs epitaxial layers with an uncovered surface and that covered with an AlN film and subsequent annealing are studied. The ion energies and the implantation doses are chosen so that the nitrogen-atom concentration profiles coincided in structures of both types. Rutherford proton backscattering spectra are measured in the random and channeling modes, and the concentration profiles of point defects formed are calculated for the samples under study. It is found that the implantation of nitrogen ions introduces nearly the same number of point defects into structures of both types, and the formation of an AlN film by ion-plasma sputtering is accompanied by the formation of an additional number of defects. However, the annealing of structures of both types leads to nearly the same concentrations of residual defects.

Thin nano-sized aluminum nitride films on GaAs (100) substrates with varying degrees of misorientation with respect to the <100> direction can be obtained by reactive ion-plasma deposition. It is shown that growth on substrates with different degrees of mismatch from the <100> direction leads to the growth of an AlN film with different phase composition and crystalline state. An increase in the degree of misorientation in the GaAs substrate used for growth is reflected both in the structural quality of nanoscale AlN films and in their electron structure, surface morphology, and optical properties. Thus, the management of the morphology, surface composition and optical functional characteristics of AlN/GaAs heterophase systems can be achieved by using the degree of misorientation of the GaAs substrates.

AbstractThe concentration profiles of defects produced in structures upon the implantation of nitrogen ions into GaAs epitaxial layers with an uncovered surface and that covered with an AlN film and subsequent annealing are studied. The ion energies and the implantation doses are chosen so that the nitrogen-atom concentration profiles coincided in structures of both types. Rutherford proton backscattering spectra are measured in the random and channeling modes, and the concentration profiles of point defects formed are calculated for the samples under study. It is found that the implantation of nitrogen ions introduces nearly the same number of point defects into structures of both types, and the formation of an AlN film by ion-plasma sputtering is accompanied by the formation of an additional number of defects. However, the annealing of structures of both types leads to nearly the same concentrations of residual defects.

A study of the surface topography and optical characteristics of thin AlN films used as passivating and antireflection coatings deposited on n-GaAs (100) substrates by reactive ion-plasma sputtering is reported. It was found that the process conditions affect the structure and the optical characteristics of the films, which makes it possible to obtain coatings with prescribed parameters. An analysis of the results furnished by ellipsometry and atomic-force microscopy of the surface shows that the refractive index of the films is correlated with the surface structure.

Thin AlN nanofilms are produced by reactive ion-plasma deposition onto GaAs(100) substrates misoriented with respect to the 〈100〉 direction to different degrees. It is shown that growth on substrates misoriented with respect to the 〈100〉 direction to different degrees results in the formation of AlN films with different phase compositions and crystal states. An increase in the degree of misorientation of the GaAs(100) substrate used for growth influences both the structural quality of AlN nanofilms and their electronic structure, surface morphology, and optical properties. Thus, the morphology, surface composition, and optical functional characteristics of AlN/GaAs(100) heterophase systems can be controlled using differently misoriented GaAs(100) substrates.

The facets of high-power AlGaAs/GaAs semiconductor lasers were coated with thin dielectric AlN films using reactive ion-plasma technique. The refractive indices of the films were measured by the ellipsometry. It is shown the technique makes it possible to obtain AlN films with a refractive index close to that of a single-crystal material. The scanning probe microscopy was used to estimate the surface roughness of the films. The comparative results of the aging tests of lasers based on the same laser heterostructure with SiO2 and AlN coatings on their facets are presented.

AbstractMathematical simulation and experiments are used to study plastic strain in nickel [001] single crystals. It is shown that the crystal exhibits self-organization of plastic strain at all scales, and the most developed effect is observed at the microlevel. Processes of self-organization of plastic strain are determined for micro- and mesolevels. At such levels, the processes involve correlated creation and annihilation of dislocations and correlated shear in parallel gliding planes, respectively. Owing to the above processes, the strain components are quasi-periodically distributed over the face, so that crystal integrity is maintained under load.

AbstractA study of the surface topography and optical characteristics of thin AlN films used as passivating and antireflection coatings deposited on n -GaAs (100) substrates by reactive ion-plasma sputtering is reported. It was found that the process conditions affect the structure and the optical characteristics of the films, which makes it possible to obtain coatings with prescribed parameters. An analysis of the results furnished by ellipsometry and atomic-force microscopy of the surface shows that the refractive index of the films is correlated with the surface structure.

The paper presents studies of the structural and optical properties of AlN thin films grown on an AlGaAs/GaAs semiconductor laser heterostructure with the use of preliminary ionic surface cleaning and without it. After cleavage of the heterostructure, a natural surface oxide forms on the facet. In the paper, the ionic etching regime providing the removal of the surface oxide layer without significant defects in the semiconductor heterostructure is determined.