Structural and photoelectric properties of p-i-n photodiodes based on GeSiSn/Si multiple quantum dots both on Si and silicon-on-insulator (SOI) substrates were investigated. Elastic strained state of grown films was demonstrated by x-ray diffractometry. Annealing of p-i-n structures before the mesa fabrication can improve the ideality factor of current-voltage characteristics. The lowest dark current density of p-i-n photodiodes based on quantum dots at the reverse bias of 1 V reaches the value of 0.8 mA/cm2. The cutoff wavelength shifts to the long-wavelength region with the Sn content increase. Maximum cutoff wavelength value is found to be 2.6 μm. Moreover, multilayer periodic structures with GeSiSn/Ge quantum wells and GeSiSn relaxed layers on Ge substrates were obtained. Reciprocal space maps were used to study the strained state of GeSiSn layers. The optimal growth parameters were determined to obtain slightly relaxed GeSiSn layers. Designed p-i-n photodiodes based on these structures demonstrated the minimal dark current density of 0.7 mA/cm2 and the cutoff wavelength of about 2 μm.

The study presents an investigation of the optical properties of rectangular -shaped aluminum nanoantenna arrays formed on the surface of an emitting GeSiSn/Si heterostructure with multiple quantum wells. The positions of the localized surface plasmon resonance modes excited along the long ( L ) and short ( S ) sides of the examined nanoantennas are determined utilizing the technique of Fourier -transform infrared reflectance anisotropy spectroscopy. Experimental results demonstrate that both L - and S -modes are located in the near -infrared range, and as the lateral dimensions of the nanoantennas increase, the modes' positions shift towards lower energies with an increase in the intensity of the resonance. The S -mode appears in the spectra as an overlay on the more pronounced L -mode with an intensity an order of magnitude lower. The geometry of the nanoantennas arrays with the resonance position near the photoluminescence peak of Ge 0.84 Si 0.076 Sn 0.084 /Si heterostructures ( E approximate to 0.65 eV) is characterized.

Studies of the optical absorption in the near-IR range of GeSn and GeSiSn layers of various compositions with a silicon content of up to 63% and tin up to 14% grown by molecular beam epitaxy are carried out. Two series of samples obtained on a nanostructured faceted surface and on a Si(100) surface were studied. It was found that at a telecommunication wavelength of 1.55 μm, the value of the GeSiSn absorption coefficient exceeds the value for Ge by more than 4 times. The bandgap values of GeSiSn with different compositions are determined. A good quantitative agreement of the calculated and experimental bandgap values and a qualitative agreement of the optical absorption spectra were obtained.

The work demonstrates the use of photomodulation FTIR spectroscopy to study structures containing epitaxial layers of GeSn and GeSiSn in the temperature range of 79-180 K. The photoreflectance method has enabled observation of direct interband transitions, and evaluation of the impact of temperature variation and mechanical strain on their energy values.

The current-voltage (I-V) characteristics and spectral dependences of the photocurrent of p-i-n structures, including GeSiSn/Si multiple quantum wells (MQWs) with the Sn content up to 15%, are studied. It is shown that the increase in the Sn content from 4.5 to 13% leads to a gradual increase in the dark current density from 6x10-6 A/cm2 to 5x10-5 A/cm2 at the reverse bias of 1 V. The further rise in the Sn content to 15% results in the increase of the dark current density to 5x10-4 A/cm2, which is an order of magnitude lower than the known values for GeSn-based photodiodes. The shift of the cutoff wavelength of the photoresponse with the Sn content increase in heterostructures is demonstrated. The photoresponse spectrum of the detector extends up to wavelengths of larger than 2 & mu;m at the Sn content of more than 10%.

Interband photoluminescence was obtained for structures with multiple quantum wells (MQWs) with different content of germanium and tin. Peak position in photoluminescence spectra obtained from the MQW of Ge _0.93-x Si _x Sn _0.07 /Si shifts to the long wavelength region with an increase in the Ge content in the solid solution and is observed in the energy range 0.85-0.68 eV for the germanium content from 30 to 78 % . Thus, the shift of the peak along the wavelength was observed from 1.46 to 1.82 μ m, and the total spectral range of MQW luminescence covered by these structures was 1.3–2.1 μ m. An even more significant shift of the MQW photoluminescence peak to the long-wavelength region was achieved by increasing the tin content. Increasing the fraction of Sn from 7 to 14 % while keeping the 30 % Ge fraction constant led to a shift of the peak from 0.85 to 0.75 eV. A simultaneous increase in the content of both tin and germanium in the solid solution (up to 14 and 79 μ m. A sharp ‘‘red’’ shift in the position of the photoluminescence peak with increasing temperature was discovered and its value reached 50 meV when the sample heating temperature was changed from 11 to 60–80 K. Such a significant shift in the position of the MQW photoluminescence peak is explained within the framework of a model that assumes that at low temperatures, charge carriers are randomly localized on spatial inhomogeneities of the MQW, and as the temperature increases, they are redistributed and transition to a thermodynamically equilibrium state with the lowest energy.

The results of studying the photoluminescence of nanoheterostructures with multiple Ge1-x-ySixSny/Si quantum wells grown by molecular beam epitaxy on silicon substrates and annealed at different temperatures are presented. As a result of the annealing of the structures, a multifold increase in the intensity of the luminescence peak close in energy to the optical transitions within the multiple quantum wells is observed. The optimal annealing temperature and duration are determined in terms of the intensity of photoluminescence. The luminescent properties of a series of annealed Ge0.93-xSixSn0.07/Si structures with different Ge compositions are investigated. As a result, a shift of the low-temperature photoluminescence peak towards lower energies with an increase in the fraction of germanium in the alloy composition is shown. Thus, the possibility of controlling the luminescence spectrum of Ge0.93-xSixSn0.07/Si nanoheterostructures in the wavelength range of 1.3 −2.0 µm is demonstrated.

This work investigates the luminescence properties of pseudomorphic nanostructures with Ge 1- x - y Si x Sn y /Si superlattices (SL) grown on silicon substrates by molecular beam epitaxy. It was shown that the addition of Sn ( y = 0.07) to the alloy layers within the structures results in a significant shift of the photoluminescence (PL) spectra towards longer wavelengths (2.0-3.5 μm) compared to similar Ge 0.7 Si 0.3 /Si superlattices. A series of experiments involving etching the structures to different depths have shown that the observed photoluminescence occurs exactly in the Ge 1- x - y Si x Sn y /Si SL region, with the sublinear nature of the PL power dependence indicating the probable participation of defects in radiative recombination. A significant increase in low-temperature PL was observed with a decrease in the thickness of narrow-gap SL layers from 6 to 2 nm, as well as with an increase in the number of superlattice periods from 10 to 30. The obtained structures exhibit relatively good temperature stability of luminescence, which is preserved up to 160 K. Thus, the current work demonstrates the possibility of creating mid-wave IR emitting epitaxial structures on silicon substrates.

The results of studying the photoluminescence of nanoheterostructures with multiple Ge1-x-ySixSny/Si quantum wells grown by molecular beam epitaxy on silicon substrates and annealed at different temperatures are presented. As a result of the annealing of the structures, a multifold increase in the intensity of the luminescence peak close in energy to the optical transitions within the multiple quantum wells is observed. The optimal annealing temperature and duration are determined in terms of the intensity of photoluminescence. The luminescent properties of a series of annealed Ge0.93-xSixSn0.07/Si structures with different Ge compositions are investigated. As a result, a shift of the low-temperature photoluminescence peak towards lower energies with an increase in the fraction of germanium in the alloy composition is shown. Thus, the possibility of controlling the luminescence spectrum of Ge0.93-xSixSn0.07/Si nanoheterostructures in the wavelength range of 1.3-2.0 μm is demonstrated. Keywords: nanoheterostructures, photoluminescence, molecular beam epitaxy, infrared emitters.

The results of investigating the generation of strained nanoheterostructures based on compounds with materials of group IV (Ge, Si, Sn) are presented. It is established how silver, tin, and lead atoms diffuse over the surface and what temperature dependences of diffusion coefficients are specific to atoms of these elements. It is shown that the diffusion of silver, tin, and lead atoms follows the mechanism of solid-phase wetting with generation of surface phases. The experimental data are provided that indicate the dominating role of edge dislocations and dislocation complexes of edge type in relaxation of Ge/Ge $${}_{0.5}$$ Si $${}_{0.5}$$ /Si(001) heterostructure. Tin-rich islands with Si pedestal on Si(001) substrate were obtained by the molecular beam epitaxy method. Firstly, the Sn film was applied on the Si surface. During the subsequent annealing an array of Sn islands, which were further used as catalysts for growing nanoobjects, was formed. Tin-rich islands with Si pedestal are formed after deposition of silicon at temperatures of 300–450 $${}^{\circ}$$ C on the surface with Sn islands. The growth of islands with pedestal occurred by the vapor–liquid–crystal mechanism. Intense photoluminescence was revealed from the tin-rich islands with Si pedestals in the wavelength range 1.3–1.7 $$\mu$$ m.

The growth of multilayer structures with Ge0.3Si0.7-yGey/Si heterojunction at tin content from 0 to 18% was studied. The X-ray diffractometry method shows the presence of strict periodicity of layers and a high level of tin content. It has been established that GeSiSn compounds are thermally stable in the annealing temperature range of 300-550 °C. A photoluminescence signal in the infrared range of about 3 microns is observed from a structure with pseudomorphic GeSiSn layers.

В работе изучен рост многослойных периодических структур и сверхрешеток, включающих упругонапряженные слои GeSiSn с содержанием олова от 0 до 18 %. Установлена кинетическая диаграмма роста слоев GeSiSn с высоким содержанием Sn в диапазоне температур 100 – 300 °C. На основе кинетических диаграмм роста пленок GeSiSn выбиралась область толщин, соответствующая псевдоморфному состоянию. В

A hybrid material including tin oxides on the top of a Ge0.3Si0.7–ySny/Si multiple quantum well structure has been first obtained. Tin oxides such as SnO and SnO2 were formed as a result of phase transitions during the oxidation of polycrystalline tin films (β-Sn). The photoluminescence was demonstrated with a maximum intensity at about 2.34 eV, which corresponds to the band gap of SnO. The glow at the photogeneration point is seen in green. The photoluminescence from SnO is observed after the annealing in the temperature range of 300-400 °C. An increase in the annealing temperature leads to a sharp quenching of the photoluminescence. It is associated with the phase transition from SnO to SnO2. The growth of Ge0.3Si0.7–ySny/Si multilayer structures is studied at the Sn content from 0 to 18%. It was found that GeSiSn compounds are thermally stable in the annealing temperature range of 300–550°C. In addition to the photoluminescence signal in the visible range from tin oxides, the photoluminescence signal in the infrared range of about 3 μm appears. It is formed from the GeSiSn/Si structure.

The paper presents the morphological, structural, and optical properties of nanostructured SnO (x) films obtained by molecular beam epitaxy using deposition of tin in an oxygen flux on an oxidized silicon substrate as a function of the annealing temperature of the synthesized structure. The effect of annealing temperature on the structural and phase state of the films is established. The orthorhombic phase of SnO2 was observed after annealing in air at 500°C. An increase in the annealing temperature up to 800°C leads to the appearance of small fraction of the tetragonal phase of SnO2. The effect of the crystal structure on the optical properties of tin oxide films is shown. Ellipsometry revealed a sharp change in the optical constants of the film near the annealing temperature of 500°C. The observed wide absorption band in the range 1.9–3.4 eV is apparently associated with small (approximately 1%) amount of unoxidized metal Sn clusters. Photoluminescence in a wide range of 450–850 nm with a maximum at ~600 nm is observed. An increase in the annealing temperature from 500 to 800°С leads to an increase in the PL intensity by almost a factor of 6.

The initial stages of G(1-x-y)Si(x)Sn(y) film growth on Ge substrate were investigated and the kinetic diagram of the morphological state for GeSiSn films was built. The kinetic diagram for the GeSiSn films on the Ge substrate was compared to the kinetic diagram for GeSiSn films on Si substrate. New phase diagrams of the superstructural changes on the Sn surface were obtained at different initial conditions of the Sn cover deposition. The Sn film growth was performed at room temperature and 200 degrees C. Superstructures such as (7 x 1), (8 x 1) and (10 x 1) were first obtained on the Sn surface. The phase diagrams allow for determining and controlling the surface Sn cover during the multilayer periodical structures growth, as well as demonstrating the separate interest in obtaining the epitaxial thin Sn films The multilayer structure growth with the pseudomorphic GeSiSn films on Ge and Si substrates was investigated using the phase diagrams for the superstructural changes of the Sn film and reflection high energy electron diffraction (RHEED) pattern. The rocking curves obtained by x-ray diffraction from the multilayer structures containing the GeSiSn layers with the Sn content up to 14% on the Ge and Si substrates demonstrate the pseudomorphic GeSiSn film state, sharp interfaces, as well as the conservation of the periodicity and content in all periods. The comparison of band diagrams based on Ge1-x-ySixSny/Si and Ge1-x-ySixSny/Ge heterostructures was performed, and the conditions, which correspond to the transition to the direct bandgap Ge1x-ySixSny material, were determined. Based on the multilayer structures with the Ge1-x-ySixSny/Si heterojunction, p-i-n diodes were created and a vertical photocurrent was measured in the photovoltaic regime at zero bias. The p-i-n diode photocurrent extends at least to 4 mu m.

The Sn-rich islands with a Si pedestal on the Si(1 0 0) substrate were obtained by the molecular-beam epitaxy technique. Initially, Sn films of different thicknesses were formed on the Si surface and then annealed to create the Sn island arrays, which were used as nanoobject growth catalysts. The Sn island density reaches up to 6 x 10(9) cm(-2), whereas the Sn island sizes are changed in the range of 40-180 nm. The Sn-rich islands with the Si pedestal were first appeared after the Si deposition on the surface with the Sn islands in the temperature range of 300-450 degrees C. The new obtained nanostructures have the island density up to 4 x 10(8) cm(-2) and the island sizes, which varied from 60 to 400 nm. The island growth with the pedestal occurred on the vapor-liquid-solid mechanism. The chemical analysis of the samples carried out using the energy-dispersive X-ray spectroscopy indicated the presence of the Sn-rich region on the top of nanoobjects. The intense photoluminescence from the Sn-rich islands with the Si pedestal was detected. The photoluminescence peak takes place at 1.55 mu m.

The formation of pseudomorphous GeSiSn layers directly on Si have been investigated. The transition from two-dimensional growth regime to three-dimensional of the GeSiSn film on Si(100) was studied for different mismatch with silicon and growth temperatures. A possibility of synthesis of multilayer structures by molecular beam epitaxy was shown. The crystal lattice constants were determined using the high-resolution transmission electron microscopy and X-ray diffractometry. The p-i-n-diodes based on multilayer GeSiSn/Si structures were created which demonstrated the photoresponse increasing by several orders of magnitude in comparison the Sn-free structures at an increase in the Sn content. Nanostructures based on GeSiSn layers have demonstrated the photoluminescence at 0.6−0.85 eV.

Nucleation of Ge islands on a stepped Si(100) surface is studied. It is shown by diffraction of fast electrons that at a temperature of 600°C, constant flux of Si, and deposition rate of 0.652 Å/s, a series of the 1×2 superstructure reflections completely disappears, if the Si (100) substrate deviated by an angle of 0.35° to the (111) face is preliminarily heated to 1000°C. The disappearance of the 1×2 superstructure reflexes is due to the transition from the surface with monoatomic steps to that with diatomic ones. Investigations of the Ge islands’ growth were carried out on the Si(100) surface preliminarily annealed at temperatures of 800 and 1000°C. It is shown that the islands tend to nucleate at the step edges.

One of the most promising technologies in semiconductor electronics is molecular beam epitaxy, which is a successive deposition on the semiconductor substrate of layers of atomic thickness of various materials from molecular beams in ultra-high vacuum (residual gas pressure less than 10 -8 Pa).During this process (in situ), molecular beams and nanoheterostructures are diagnosed.Creation of high-performance micro-, nano-and photoelectronics devices based on semiconductor nanoheterostructures consisting of III-V compounds grown on cheap Si substrates is one of the priorities of modern semiconductor materials science.The solution this problem is extremely important for the development of high-performance photovoltaics.Modern high-performance solar cells are complex multilayer heterosystems with an efficiency of up to 45 % at a concentration of solar radiation in several hundred suns.They consist of three main p-n junctions made of Ge, InGaAs, InGaP connected in series by tunnel diodes.This article presents an automated compact plant of new generation of molecular beam epitaxy for epitaxy of films and nanostructures based on Si, Ge and (or) compounds of A3B5 type, developed at the Rzhanov Institute of Semiconductor Physics of the Siberian Branch of RAS.