Self-organized nanosize InP and InAsP clusters obtained by metalorganic compound hydride epitaxy

Results are presented of investigations of the growth of self-organizing nanosize InP and InAsP clusters in an In_0.5Ga_0.5P matrix. The structure was characterized by low-temperature photoluminescence and transmission electron microscopy. The photoluminescence measurements revealed highly efficient radiative recombination from the quantum dots and indicated that the structures were of good optical quality. The average density and size of the InP clusters, determined from the results of the transmission electron microscope measurements, are 3×10⁹ cm⁻² and 80 nm, respectively. Pis’ma Zh. Tekh. Fiz. 24, 1–7 (August 26, 1998)     

Investigation of strained InxGa1−x As/InP quantum wells fabricated by metalorganic compound hydride epitaxy

An investigation was made of the possibility of using reduced-pressure MOC hydride epitaxy to fabricate highly strained (compressive stress) In_xGa_1−x As/In_0.53Ga_0.47As quantum wells on indium phosphide (100) substrates. The photoluminescence properties of these heterostructures were investigated. It was shown that these heterostructures are potentially useful for laser diodes emitting in the 1.5–2 μm range, which is important for environmental monitoring. Pis’ma Zh. Tekh. Fiz. 24, 46–51 (November 26, 1998)     

Application of silicon carbide fibers for increasing the service parameters of abrasive cutting wheels

Abrasive cutting wheels reinforced with silicon carbide fibers are produced and tested. Their wear resistance for cutting steel pipes is much greater than in commercially produced wheels reinforced by glass network. The use of silicon carbide fibers makes it possible to produce wheels 1.0–1.5 mm in thickness while analogous commercial wheels are only 3.0 mm in thickness. Decreasing the thickness of the wheel helps save a scarce material, reduces the power rating of the equipment, and decreases the width of the cut.Translated from Poroshkovaya Metallurgiya, No. 10, pp. 91–93, October, 1992.     

Spontaneously assembling periodic composition-modulated InGaAsP structures

It is established theoretically and experimentally that in certain temperature and composition ranges the solid solutions InGaAsP comprise a system of strained, alternating (in mutually perpendicular directions [100] and [010]) domains of a solid solution with two different compositions and different lattice constants. The domains are clearly seen at the surface of an epitaxial film and wash out into its depth in the direction of the substrate. The data obtained most likely show spinodal decomposition of InGaAsP solid solutions in the experimental samples. Fiz. Tekh. Poluprovodn. 33, 1108–1110 (September 1999)     

Epitaxial deposition of InGaAsP solid solutions in the miscibility gap

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. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 11, 2000, pp. 1307–1310. Original Russian Text Copyright ? 2000 by Vavilova, Kapitonov, Murashova, Tarasov.     

Selection of the heating method of semiconductor devices during their testing in a high-conductivity state

Possible heating methods of power semiconductor devices during their testing in a high-conductivity state are discussed. It is shown that the diffusion capacitance of the p–n junction has a significant effect on measurements of device parameters. The effect of the diffusion capacitance on the results of testing of power semiconductor devices at various shapes of heating-current pulses was investigated. Conclusions on the possibility of using current pulses of various shapes for testing power semiconductor devices in the highconductivity state are drawn.     

MOCVD-grown InGaAs/GaAs/AlGaAs laser structures with a broad-area contact

A metal-organic chemical vapor deposition (MOCVD) technique is developed for a diode laser heterostructure in a system of InGaAs/GaAs/AlGaAs solid solutions; the optimal sizes and the doping profile of the structure are determined to minimize the internal optical losses. Mesa-strip diode lasers with a threshold density of current J _th=150–200 A/cm², internal optical loss factor α_i=1.6–1.9 cm^?1, and an internal quantum yield η_i=85–95% were fabricated. In the continuous lasing mode of a diode laser with a 100-µm-wide aperture and a wavelength of 0.98 µm, the optical power output was as high as 6.5 W and was limited by the catastrophic optical degradation of mirrors. The radiation divergence in the plane normal to the p-n junction amounts to θ_⊥. The use of wide-gap waveguide layers, which deepens the potential electron well in the active region, is shown to reduce the temperature sensitivity of the InGaAs/GaAs/AlGaAs laser heterostructures in the temperature range from 0 to 70°C.     

AlGaAs/GaAs diode lasers (1020–1100 nm) with an asymmetric broadened single transverse mode waveguide

Approaches to the development of laser heterostructures with a broadened single-mode waveguide are studied theoretically and experimentally. It is shown that the use of n- and p-type emitters with different refractive-index values ensures lasing in the fundamental mode only, if the thickness of the waveguide layer is 2 μm. The studied semiconductor lasers fabricated using the developed heterostructure feature internal optical losses amounting to 0.6 cm^?1; the divergence in the plane perpendicular to the p-n junction is 23°. In the continuous lasing mode at room temperature, a linear power-current characteristic is obtained at an output optical power as high as 7 W.     

Saturation of light-current characteristics of high-power laser diodes (λ = 1.0–1.8 μm) under pulse operation

Spectral and light-current characteristics of separate-confinement lasers that are based on InAl-GaAs/InP and InGaAsP/InP alloys and emit in the wavelength range of 1.5–1.8 μm are studied at high excitation levels (up to 80 kA/cm²) in pulse operation (100 ns, 10 kHz). It is shown that the peak intensity in the stimulated-emission spectrum saturates as the pump current is increased. Further increase in the emitted power is attained owing to the emission-spectrum broadening to shorter wavelengths, similar to lasers on the GaAs substrates (λ = 1.04 μm). It is established experimentally that the broadening of the stimulated-emission spectrum to shorter wavelengths is caused by an increase in the threshold current and by an increase in the charge-carrier concentration in the active region. This concentration increases by a factor of 6–7 beyond the lasing threshold and can be as high as 10¹⁹ cm^?3 in pulse operation. It is shown that saturation of the light-current characteristics in pulse operation takes place in the InAlGaAs/InP and InGaAsP/InP lasers as the pump current is increased. It is shown experimentally that there is a correlation between saturation of the light-current characteristic and an increase in the threshold current in the active region. An increase in the charge-carrier concentration and gradual filling of the active region and waveguide layers with electrons are observed as the pump current is increased; stimulated emission from the waveguide is observed at high pump currents.     

Record power characteristics of InGaAs/AlGaAs/GaAs heterostructure lasers

Continuous-wave output powers of 9.2 W at a constant heatsink temperature of 10°C and 12.2 W at a stabilized temperature of the active region have been obtained on an InGaAs/AlGaAs laser with a 0.4-μm-thick waveguide, operating at 1.03 μm. Record-breaking output mirror power densities of, respectively, 29.9 and 40 MW/cm² have been achieved without catastrophic optical mirror damage in the two temperature-stabilization regimes. A maximum power conversion efficiency of 66% has been achieved in a laser with a cavity length of 2 mm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 3, 2001, pp. 380–384. Original Russian Text Copyright ? 2001 by Livshits, Egorov, Kochnev, Kapitonov, Lantratov, Ledentsov, Nalyot, Tarasov. Deceased.