The technology for production one and two-cascade power laser converters was presented in this paper. According to the measurement results of the grown samples, an efficiency of 34.5% was achieved. A promising design of a cascade photoelectric converter is proposed, in which the cascades are connected with using conduction channels based on GaP microcrystallites.
The influence of methane plasma parameters on the deposition rate and on the content of the hydrogen and the sp3-carbon fraction in hydrogenated diamond-like carbon films (DLC) was investigated. It was shown that the proportion of the sp3-carbon fraction mainly depends on the inductive power and the argon addition to the plasma; the latter also contributes to a decrease of hydrogen in the films.
The problems of in situ ellipsometric control during the growth of ZnTe and CdTe buffer layers intended for cadmium-mercury-tellurium epitaxy are considered. It has been established that for 20 nm ZnTe layers the spectral dependences of the optical constants near the absorption edge are smoothed, which indicates the presence of structural defects in the film. It has been shown that the microrelief of the CdTe growth surface is a criterion for the structural perfection of the layers and can be measured using an ellipsometer both at the early stages and during steady-state growth.
The capture times of holes to the shallow excited levels of neutral mercury vacancy via acoustic phonon emission are calculated for Hg1 – xCdxTe, as well as the transition times of holes from shallow localized levels to the continuum of the valence band at different temperatures. Due to the redistribution of carriers in the valence band with temperature, the time of carrier capture to the localized levels of the neutral vacancy increases, and the time of reionization to the continuum decreases. Based on the calculation results, a model is proposed to describe the temperature quenching of photoluminescence caused by radiative transitions between the localized states of holes on a neutral mercury vacancy.
Experimental results on the observation of terahertz luminescence under optical excitation of silicon doped with neutral helium-like magnesium donors under photoionization conditions under uniaxial stress are presented. Possible options for creating stimulated radiation sources based on Si:Mg under optical excitation are considered. The possibility of obtaining inversion at the lowest odd level and significant gain coefficients is difficult due to the rather short relaxation time of the 2p0 level. The possibility of using an alternative inversion mechanism presupposes knowledge of relaxation routes. The mechanism of stimulated Raman scattering is theoretically considered and it is shown that terahertz stimulated radiation with optical excitation of double magnesium donors in silicon can be achieved using the mechanism of electronic-type Raman scattering.
We find and study the generation regime of microwave waves in a model resonator cavity based on an array of ordered semiconductor carbon nanotubes. Within the framework of the phenomenological approach, the Gunn effect was discovered for aligned carbon nanotubes with a length of 25–150 μm, the influence of the main parameters (changes in the electric field, the distance between the electrodes, the voltage at the contacts, etc.) was studied and it was shown that the electronic efficiency during lasing can reach 13%. The results obtained can be used to design new resonator structures such as compact microwave amplifiers and emitters based on ordered arrays of nanotubes.
Composite materials Bi2Te2.7Se0.3/Teδ with varying concentration (δ = 0.15, 0.2, 0.25, and 0.3) are obtained by the solvothermal synthesis of initial powders and their subsequent spark plasma sintering. During the sintering process, the samples are textured, as a result of which lamellar grains are arranged in layers perpendicular to the direction of the application of pressure during sintering (the direction of the texture axis). Upon magnification, the concentration of superstoichiometric tellurium decreases the degree of texturing. The concentration of tellurium does not affect the average grain size. Superstoichiometric tellurium is distributed along the grain boundaries, as a result of which a structure characteristic of composite materials is formed. The release of tellurium at the grain boundaries leads to a change in the thermoelectric properties of the obtained materials. The electrical resistivity naturally increases, and the total thermal conductivity decreases with an increase in the concentration of superstoichiometric tellurium.
The static and dynamic characteristics of waveguide photodetectors with an absorbing region based on InGaAs/GaAs quantum well-dots were studied at room temperature. The absorption band of InGaAs/GaAs quantum well-dots is in the spectral range from 900 to 1100 nm. The waveguide photodetectors have a width of 50 μm and a length of the absorbing region from 92 μm to 400 μm. A low dark current density (1.1 and 22 μA/cm2 at –1 and –20 V) and cut off frequency of 5.6 GHz, limited by the time constant of a parasitic equivalent electric RC-circuit, were obtained.
epitaxial layers of AlxGa1–xAs1–y Sby with an aluminum content x ~ 60% and antimony content y ~ 3% were successfully grown by molecular-beam epitaxy at low temperature. A developed system of AsSb nanoinclusions was formed in the semiconductor matrix by subsequent annealing. The extended transparency window of the obtained metamaterial allows us to document the absorption of light near the interband absorption edge of the AlxGa1–xAs1–ySby semiconductor matrix. Parameters of the observed extinction band allow us to attribute the optical absorption to the plasmon resonance in the system of AsSb nanoinclusions.
A model is proposed that makes it possible to analytically analyze the speed performance of a waveguide p–i–n photodiode with a light-absorbing region representing a multilayered array of quantum dots separated by undoped spacers. It is shown that there is an optimal number of layers of quantum dots, as well as an optimal thickness of the spacers, which provide the widest bandwidth. The possibility of achieving a frequency range (at the level of –3 dB) above 20 GHz for waveguide photodiodes based on InGaAs/GaAs quantum well-dots is shown.
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