Heterostructures with an active region based on GaAs/Ge/GaAs layers are of interest for creating terahertz devices and topological insulators. The optical and electrical properties of such devices depend, to a great extent, on the conditions of their synthesis. In this work, the structure of GaAs layers in GaAs/Ge/GaAs heterostructures grown on a GaAs(001) substrate by molecular-beam epitaxy under process conditions providing a 90° rotation of the crystal lattices of the upper and lower GaAs layers in samples of one type and no rotation in samples of the other type is examined. The synthesized heterostructures are studied by transmission electron microscopy and electron-diffraction analysis using thin cross-sectional foils prepared by the focused-ion-beam method. It is found that the GaAs/Ge/GaAs layers in samples of both types have a high crystal quality, but stacking faults and antiphase domains are formed in the GaAs layers located above the Ge layer. The relative orientation of the upper and lower GaAs layers in GaAs/Ge/GaAs is identified by comparing the intensity distributions in the disks 002̅ and 002 in the diffraction patterns obtained by convergent-beam electron diffraction. It is demonstrated by simulating the patterns that the orientation of the sample along the [310] zone axis is optimum for detecting differences between the diffraction patterns on pseudo-forbidden disks 002̅ and 002. The experimental diffraction patterns obtained under such conditions confirm the identical orientation of the crystal lattices of the upper and lower GaAs layers in samples of one type and the rotation of the lattices of these layers by 90° about the [001] direction in the samples of the other type.

Transmission electron microscopy is used to study the formation of InGaAs/GaAs quantum dots by molecular beam epitaxy under the influence of a Bi vapor flow on the growth surface at different temperatures of the GaAs substrate. Mixed-dimensional nanostructures (0D/2D) are found. Energy-dispersive X-ray spectroscopy demonstrates that Bi acts as a surfactant and is not trapped by the growing layers.

The formation of InGaAs/GaAs quantum dots by molecular beam epitaxy is studied under the effect of Bi vapor flow on the growth surface at different temperatures of the GaAs substrate. It is shown that Bi acts as a surfactant, lowering the temperature of the formation of quantum dots by about 50°C.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation I. P. Kazakov, K. V. Shishakov; Research on the temperature dependence of the calibration functions of the Trihedron accelerometers. AIP Conf. Proc. 27 February 2023; 2605 (1): 020009. https://doi.org/10.1063/5.0111045 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Transmission electron microscopy is used to study the crystalline granular structure of a low-temperature GaAs epitaxial layer grown on a Si(100) substrate. The grain sizes are determined using a series of electron-microscopy images acquired in a small range of tilt angles of a plan-view specimen around the Si[110] and Si[1 $$\bar {1}$$ 0] directions. The grain boundaries can be unambiguously identified by the digital processing of images obtained by bright-field transmission electron microscopy and using electrons scattered at small angles by scanning transmission electron microscopy. The effectiveness of a semi-automated method for detecting grain boundaries is demonstrated; the method is used to plot and analyze a histogram of the grain distribution by their lateral sizes.

The results of investigations of solar-blind image converter tubes (ICTs), sensitive in the vacuum-ultraviolet (VUV) spectral range are presented. Sensitive-conversion layers of photocathodes based on boron-doped polycrystalline diamond films were grown up on sapphire substrates for the first time. Electron flow multipliers (EFMs) were fabricated in the form of diamond grid. Solar-blind VUV ICTs without the EFM are characterized by spectral sensitivity range of 180...250 nm, estimate of the threshold sensitivity value -10-9 W/Hz0.5 and current sensitivity -12 - 15 mA/W. Solar-blind VUV ICTs comprising the electron flow multipliers are characterized by extended spectral sensitivity range of 180...270 nm, improved estimate of the threshold sensitivity value 10-11... 5 x 10-12 W/Hz 0.5 and current sensitivity 50 mA/W.

Статья посвящена построению калибровочных функций углового положения конструктивно выполненных автономных блоков из трех ортогонально расположенных акселерометров в рамках технологической процедуры их статической калибровки для повышения точности определения проекций силы тяжести на координаты связанной с объектами пространственно-ортогональной системы координат. Для этого использованы два варианта угловых преобразований осей координат: в углах Эйлера и в самолетных углах. При проведении контроля и диагностики точности показаний акселерометров в триэдре рекомендуется проводить измерения вектора силы тяжести, выполняя полные обороты по какому-либо одному из углов.Математическая основа для построения функций системной калибровки триэдра акселерометров описана в рамках процедур перепроецирования измерительных сигналов на «правильные» ортогональные оси. Приведены получающиеся линейные и нелинейные калибровочные функции. Рассмотрены варианты улучшения обусловленности вычислительных алгоритмов для идентификации линейных и нелинейных калибровочных функций углового положения триэдра акселерометров.Приведены вычислительно облегченные методики, предназначенные для серийной калибровки триэдров акселерометров. В них использовано разложение показаний акселерометров вдоль осей «искаженной» системы координат на оси «правильной» ортогональной системы координат.В качестве примера приведено сравнение результатов линейной и нелинейной калибровки блока из трех акселерометров АК-15 на стенде. Показано, что для выбранных прецизионных акселерометров вполне достаточно использовать линейную методику калибровки.

The results of investigations of solar-blind image converter tubes (ICTs), sensitive in the ultraviolet spectral range are presented. Photocathodes sensitive layers of the ICT are based on boron-doped polycrystalline diamond films were grown up on sapphire substrates for the first time. Spectral range of the ICT sensitivity is 180…250 nm, the threshold sensitivity value without the electron flow multiplier ~ 10-9 W/Hz0.5 and spectral sensitivity ~ 12 - 15 mA/W.

Ultraviolet solar-blind electron-optical converters with photocathode sensor layers made of polycrystalline boron-doped diamond films, which were for the first time grown on sapphire, are studied. The spectral sensitivity range of the obtained converters is 180–250 nm, the threshold sensitivity without the electron flux multiplier is no worse than ∼10–9 W/Hz0.5, and the spectral sensitivity is 12–15 mA/W.

The GaAs layer turn on Ge at a right angle in the substrate plane was studied by high-energy electron diffraction and transmission electron microscopy methods when growing GaAs/Ge/GaAs heterostructures using individual molecular-beam epitaxy systems for GaAs and Ge, with sample transfer through atmosphere.

Herein we report the studies on the GaBiAs terahertz emitters. The molecular beam epitaxy grown thin films were subjected to structural and optical characterization. Inhomogeneity of Bi concentration in the samples is confirmed by XRD, PL and EDS studies. Investigations on the generation characteristics of the fabricated bow-tie photoconductive antennas were carried out via the Fourier Transform Infrared Spectroscopy. The collected data indicate a pattern of change in the shape of the spectra with increasing bismuth concentration, namely, a sharp drop in the low-frequency part (0.1-0.2 THz) simultaneously with a noticeable increase in intensity in the range 0.3-1 THz with a pronounced maximum at frequencies of similar to 0.4 THz. The deterioration of the THz power to average photocurrent ratio can be explained by a general decrease in the electron mobility, caused both by a large number of structural defects and by a large local heating of the crystal.

In this report, we present our studies on multi-barrier Al0.3Ga0.7As/GaAs quantum well (QW) system to obtain a given subband position in a quantum well to be used in quantum well solar cells to enhance efficiency in conventional solar cells by extend

Single quantum wells in the system Si1_xGex/Si with x < 0.1 are grown by molecular-beam epitaxy in the mode of periodic Ge molecular flow interruption during the formation of the alloy layer. It allowed an increase in the operating current of the source electron gun, which provided a more stable molecular Ge flow. The grown heterostructures are studied by transmission scanning electron microscopy methods

Single quantum wells in the Si1-xGex/Si (x < 0.1) system grown in the mode of molecular Ge flow modulation in forming the solid solution layer are studied. The grown heterostructures are investigated by the low-temperature photoluminescence method, and their properties were compared with the properties of similar heterostructures grown without modulation of the Ge molecular flow. It is shown that modulation of the Ge flow has almost no effect on the spectral properties of the quantum wells.

The mechanical strains and densities of surface charge states in GaAs layers grown by low-temperature (LT) molecular-beam epitaxy on Si(100) and GaAs(100) substrates are investigated by photoreflectance spectroscopy. Lines corresponding to the fundamental transition ( E g ) and the transition between the conduction band and spin-orbit-split valence subband ( E g + Δ SO ) in GaAs are observed in the photoreflectance spectra of Si/LT-GaAs structures at 1.37 and 1.82 eV, respectively. They are shifted to lower and higher energies, respectively, relative to the corresponding lines in GaAs/LT-GaAs structures. Comparing the spectra of the Si/LT-GaAs and GaAs/LT-GaAs structures, it is possible to estimate mechanical strains in LT-GaAs layers grown on Si (by analyzing the spectral-line shifts) and the density of charge-carrier states at the GaAs/Si heterointerface (by analyzing the period of Franz–Keldysh oscillations).

AbstractThe mechanical strains and densities of surface charge states in GaAs layers grown by low-temperature (LT) molecular-beam epitaxy on Si(100) and GaAs(100) substrates are investigated by photoreflectance spectroscopy. Lines corresponding to the fundamental transition ( E _ g ) and the transition between the conduction band and spin-orbit-split valence subband ( E _ g + Δ_ SO ) in GaAs are observed in the photoreflectance spectra of Si/LT-GaAs structures at 1.37 and 1.82 eV, respectively. They are shifted to lower and higher energies, respectively, relative to the corresponding lines in GaAs/LT-GaAs structures. Comparing the spectra of the Si/LT-GaAs and GaAs/LT-GaAs structures, it is possible to estimate mechanical strains in LT-GaAs layers grown on Si (by analyzing the spectral-line shifts) and the density of charge-carrier states at the GaAs/Si heterointerface (by analyzing the period of Franz–Keldysh oscillations).

GaAs/Ge/GaAs heterostructures with sublattice reversed GaAs on Ge epilayers grown via molecular beam epitaxy (MBE) for periodic domain inverted structures are presented. For the first time, such structures are grown in separate MBE machines for GaAs and Ge with atmospheric wafer transfer. The high quality of the heterostructures is confirmed via X-ray diffraction and photoluminescence. It is proposed that the surfactants (Bi, Sb) be used to control the nucleation of GaAs epilayers on a Ge epilayer.

GaAs/Ge/GaAs heterostructures in which GaAs layer lattices are rotated at a right angle in the substrate plane are studied. High quality of heterostructures is confirmed by X-ray diffraction and photoluminescence methods.