Investigation of the structural properties of GaAs layers grown by molecular-beam epitaxy at low temperatures

The results of an investigation of the structural perfection of GaAs epitaxial films grown by molecular-beam epitaxy at low growth temperatures (240–300 °C) and various As/Ga flux ratios (from 3 to 13) are presented. Diffraction reflection curves display characteristic features for the samples before and after annealing in the temperature range from 300 to 800 °C. Hypotheses which account for these features are advanced. The range of variation of the arsenic/gallium flux ratio, in which low-temperature growth takes place under nearly stoichiometric conditions, is established. Fiz. Tekh. Poluprovodn. 31, 1168–1170 (October 1997)     

Study of new designs for the InAlAs metamorphic buffer on GaAs substrates with distributed compensation of elastic deformations

Two new designs for a metamorphic buffer, which are modifications of the In _x Al_{1 ? x} As metamorphic buffer due to groups of layers with differing lattice parameters, are proposed and implemented. This makes it possible to affect the relaxation of the metamorphic buffer. The structural and electrical characteristics of the obtained metamorphic HEMT nanoheterostructures are also studied.     

n-AlGaAs/GaAs/n-AlGaAs double quantum wells with an AlAs barrier: Relating the cladding doping level to structural and transport properties

Double quantum wells in the form of an AlGaAs/GaAs/AlGaAs heterostructure with an AlAs barrier a few monolayers thick are fabricated by MBE. Their structural and compositional characterization is carried out by double-crystal XRD and SIMS. Electron mobility is evaluated by Hall-effect measurements for different quantum-well thicknesses. Conditions are identified under which electron mobility can be enhanced by introduction of an ultrathin barrier into a single quantum well. The findings are analyzed from the viewpoint of interface structural quality.Translated from Mikroelektronika, Vol. 34, No. 2, 2005, pp. 98–109.Original Russian Text Copyright © 2005 by Vasilevskii, Galiev, Ganin, Imamov, Klimov, Lomov, Mokerov, Saraikin, Chuev.     

Electrical and structural properties of PHEMT heterostructures based on AlGaAs/InGaAs/AlGaAs and δ-doped on two sides

The pseudomorphic AlGaAs/InGaAs/AlGaAs heterostructure δ-doped with silicon on both sides and used for fabrication of high-power transistors is optimized to obtain a high concentration n _s and mobility of two-dimensional electron gas in the quantum well (n _s ≈ 3 × 10¹² cm^?2). Electrical and structural characteristics of the samples grown by molecular-beam epitaxy with various doping levels are studied. It is shown that the mobility and concentration of electrons varies as doping level is increased and the subbands of dimensional quantization are sequentially filled. In order to analyze the distribution of electrons in subbands of the heterostructure, the Shubnikov-de Haas oscillations at the liquid helium temperature were studied. The quality of the heterostructure layers was assessed using the method of X-ray diffraction. The data of photoluminescence spectroscopy are in good agreement with the results of calculations of the band structure.     

X-ray imaging by angular raster scanning

The technology of x-ray W-Al multilayer mirrors with an angular reflection width of more than 0.4 degrees at a 1.54-A wavelength is developed. On this basis an x-ray scanner is constructed. We show experimentally the possibility of object-transfer imaging with a resolution of ~20 mum.     

A mechanism of enhancing the efficiency of solar photoelements

A principal possibility of increasing the efficiency of solar photoelements based on the effect of multiexiton generation is shown. Specific peculiarities of this effect that ensure the use of solar photoelements in the process of photoconversion are revealed. The model of the photoelement construction is proposed.     

Si/Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>x</Subscript> Superlattice Structure from X-ray-Scattering Data

An x-ray structural characterization is carried out for MBE-grown Si/Si_xGe_{1 − x} superlattices with nanometer layer thicknesses on Si(100) substrates. The characterization technique is a combination of x-ray reflectivity and x-ray diffraction in coplanar and noncoplanar arrangements. Detailed knowledge is gained of the superlattice structure, the crystalline quality of the layers, and the heterointerface morphology.__________Translated from Mikroelektronika, Vol. 34, No. 4, 2005, pp. 291–301.Original Russian Text Copyright © 2005 by Yakunin, Pashaev, Zaitsev, Subbotin, Rzaev, Imamov.     

Characterization of a Quantum Well in an Si/Si1–xGex/Si Heterostructure by X-ray Diffractometry

Rocking curves with a pronounced pendulum-solution pattern are obtained for Si_{1 – x} Ge _x /Si specimens with a single quantum well (QW) by double-crystal x-ray diffractometry. These oscillations are typical of the rocking curves for GaAs multilayers with QWs. With Si–Ge multilayers, they are obtained for the first time. The Ge depth profiles of the QW are reconstructed from the rocking curves. As a result, the thicknesses of both QW interfacial layers are estimated.