The photosensitive germanium layers on a silicon substrate have been formed by molecular beam epitaxy. The structural, optical, and photovoltaic characteristics of the films have been investigated. The data obtained confirm the possibility of using the developed Ge on Si heterostructures for fabrication of photodetectors in the spectral range of 1.3–1.55 μ m

Multistacked GeSiSn/Si quantum dot (MQD) structures of different compositions were obtained by molecular-beam epitaxy. The elastically strained state of GeSiSn/Si MQD structures was confirmed by the presence of diffraction maxima on X-ray rocking curves. The optical properties of GeSiSn/Si MQD structures were studied by Fourier transform infrared (FTIR) photoluminescence spectroscopy. The structures exhibited photoluminescence peaks in the 0.6-0.8 eV range originating from the QD region. The calculations showed that the observed peaks correspond to the radiative transition between the Delta(4) conduction band in Si and the energy level of heavy holes in the QDs. The peak positions in the PL spectra are in good correlation with the calculation results. It was demonstrated that the transition energy depends strongly on the composition and size of GeSiSn/Si QDs. The p-i-n photodiodes were developed based on the GeSiSn/Si MQD structures. The cutoff wavelength maximum reached the value of 2.65 mu m for Ge0.80Si0.11Sn0.09/Si MQD p-i-n photodiodes.

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 methods of passivating the mesastructures of photodetectors based on InSb/In _1-x Al _x Sb nBn heterostructures grown by molecular-beam epitaxy are studied. The mesastructures are formed by photolithography and liquid etching. Two different dielectrics, Al _2 O _3 and Si _3 N _4 , are used to passivate the surface of mesastructures. It is shown that the Si _3 N _4 dielectric efficiently passivates the surface of mesastructures, and the bulk current channel is predominant, whereas the surface leakage current prevails in the Al _2 O _3 passivated mesastructures. At small reverse biases, the correlation between the current and surface area of a mesastructure is violated due to the influence of defects. Modeling the current–voltage characteristics of mesastructures at 77 K shows that the major contribution to the dark current is made by the tunneling current of electrons through the In _1-x Al _x Sb barrier.

The methods of passivating the mesastructures of photodetectors based on InSb/In1-xAlxSb nBn heterostructures grown by molecular-beam epitaxy are studied. The mesastructures are formed by photolithography and liquid etching. Two different dielectrics, Al2O3 and Si3N4, are used to passivate the surface of mesastructures. It is shown that the Si3N4 dielectric efficiently passivates the surface of mesastructures, and the bulk current channel is predominant, whereas the surface leakage current prevails in the Al2O3 passivated mesastructures. At small reverse biases, the correlation between the current and surface area of a mesastructure is violated due to the influence of defects. Modeling the current-voltage characteristics of mesastructures at 77 K shows that the major contribution to the dark current is made by the tunneling current of electrons through the In1-xAlxSb barrier.

Методом молекулярно-лучевой эпитаксии сформированы фоточувствительные слои германия на кремниевой подложке. Исследованы структурные, оптические и фотоэлектрические характеристики плёнок. Полученные данные подтверждают возможность использования изготовленных гетероструктур Ge на Si для создания фотодетекторов спектрального диапазона 1,3-1,55 мкм. Photosensitive germanium layers on a silicon substrate have been formed by molecular beam epitaxy. The structural, optical and photovoltaic characteristics of the films have been investigated. The data obtained confirm the possibility of utilizing the developed Ge-on-Si heterostructures for the fabrication of photodetectors in the spectral range of 1.3-1.55 μm.

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.

GaSb films were grown by molecular beam epitaxy on vicinal Si(001) substrates with miscut angles of 6o to the (111) plane. Films were formed on AlSb(001)/Al/As/Si, AlSb(001)/Al/As/Si, GaSb(001)/Ga/P/Si and GaSb(001)/P/Ga/Si transition layers. The influence of orientation, composition, and formation conditions of transition layers on the crystal perfection and optical properties of GaSb films was studied. The GaSb film grown on the GaSb(001)/Ga/P/Si(001) transition layer has the best structural and optical properties. Keywords: molecular beam epitaxy, GaSb on Si(001), crystallographic orientation of the film, transition layers, antiphase domains, crystal perfection.

GaSb films were grown by molecular beam epitaxy on vicinal Si(001) substrates with miscut angles of 6° to the (111) plane. Films were formed on AlSb(001)/Al/As/Si, AlSb(00-1)/Al/As/Si, GaSb(00-1)/Ga/P/Si and GaSb(001)/P/Ga/Si transition layers. The influence of orientation, composition, and formation conditions of transition layers on the crystal perfection and optical properties of GaSb films was studied. The GaSb film grown on the GaSb(00-1)/Ga/P/Si(001) transition layer has the best structural and optical properties.

В данной работе было исследовано влияние отклонения подложки GaAs от сингулярной грани (100) в направлении [110] на 0°, 1°, 2°, 3°, 5° и 7° на состав твёрдых растворов GaPxAs1-x. Слой твёрдого раствора выращивался одновременно на положках всех ориентаций. Использовались потоки молекул As2 и P2, скорость роста составляла 1 МС/с, Ts = 500°С, толщина плёнки - 1 мкм. Выращенные образцы были исследованы методом высокоразрешающей рентгеновской дифрактометрии.

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.

The effect of the growth rate (flow density of In atoms) on the composition of InAsxSb1-x(100) solid solutions at molecular beam epitaxy is experimentally studied using the flows of As-2 and Sb-4 molecules. It is established that the increase in the growth rate at constant fraction of As-2 and Sb-4 molecules in the flow of molecules of group V and unchanged fraction of the flow of indium atoms to the total flow of molecules of the group V elements leads to decrease in the arsenic fraction in the solid solution. It is shown that the growth rate is an independent parameter of the process of molecular beam epitaxy determining the composition of InAsxSb1-x solid solutions. The mechanism of generation of the solid solution compound explaining the role of growth rate is proposed.

It is demonstrated that it is possible to use the ammonia molecular beam epitaxy for growing structurally perfect high-ohmic GaN layers which allow generating SiN/Al(Ga)N/GaN heterostructures for transistors with a high mobility of electrons. The growth conditions are determined for GaN layers with smooth surface morphology (with a mean-squared deviation of $${\sim}$$ 2 nm) appropriate for creating sharp heteroboundaries. The possibility of improving the crystalline perfection of GaN layer due to the use of buffer high-temperature AlN layer (with the growth temperature above 940 $${}^{\circ}$$ C) is demonstrated. It was shown that in situ surface passivation of Al(Ga)N/GaN heterostructures by the ultrathin SiN layer allows generating normally closed transistors with unprecedented low values of the current collapse ( $${\sim}1\%$$ ).

В данной работе были измерены темновые и фототоки, проведено изучение роста методом молекулярно-лучевой эпитаксии nBn-гетероструктур InSb/In1-xAlxSb на подложках InSb (001), где In1-xAlxSb является широкозонным барьером (B). Ввиду наличия рассогласования между постоянными решетки барьерного слоя и подложки InSb, необходимо определить оптимальную долю алюминия и толщину барьера, при которой слой InAlSb будет псевдоморфным, для этого была выращена серия слоев InAlSb с постоянной x=0.4, 0.3, 0.2 и переменной долей алюминия, в варизонных барьерах доля алюминия изменялась от 0.4 до 0.1 (I) и от 0.35 до 0.15 (II) в процессе роста структуры от поглощающего слоя к контактному. Контроль состояния поверхности в процессе роста проводился методом дифракции быстрых электронов. После роста был проведен анализ выращенных слоев методом рентгеновской дифракции с определением степени релаксации слоя InAlSb.

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.

GaSb films are grown by molecular-beam epitaxy using AlSb/As/Si transition layers on vicinal Si(001) substrates miscuted by 6° in (111) plane direction. The effect of GaSb films crystallographic orientation on their structural properties and surface morphology is investigated. It is found that the GaSb(00$$\bar {1}$$)/Si films are characterized by better structural perfection, a lower concentration of point defects, as well as a more planar and isotropic surface morphology as compared with the GaSb(001) films. The possible cause for the observed othernesses between the GaSb films with different orientations is an increased density of antiphase domains in GaSb(001) films. The morphological features of the grown films are caused mainly by the edges of terraces and, to a lesser extent, by anisotropy of the incorporation of Ga adatoms into the edges of the terraces.

SnO and SnO2 films were obtained on the SiO2 surface by the molecular-beam epitaxy method. The initial films are in the polycrystalline phase. The annealing of SnO(x) films at a temperature of 300 degrees C resulted in the formation of the tetragonal SnO phase. Three vibration modes E-g, A(1g), and B-1g with the frequencies of Sn-O bond vibrations of 113, 211 and similar to 360 cm(-1), respectively, which correspond to the SnO phase, were first observed by the Raman spectroscopy method. The orthorhombic SnO2 films were obtained by increasing the annealing temperature to 500 degrees C. Based on the valence band XPS (X-ray photoelectron spectroscopy) spectrum, several features with the binding energy approximately 5 eV, 7.5 eV and 11 eV, which are the same with the valence band of SnO2, were identified. The refractive index and absorption coefficient were investigated by the spectral ellipsometry technique. The high absorption coefficients correspond to the high Sn content. The film dielectric properties were revealed at the temperature higher than 300 degrees C. The refractive index values lie in the range of 1.5-2.6 for the visible spectral region. The pronounced absorption edges at 2.85 eV and 3.6 eV corresponding to those of stannous oxide (SnO) and stannic oxide (SnO2) were observed. The photoluminescence (PL) from the SnO(x) films was observed at room temperature. The increase of the annealing temperature resulted in the increase of PL intensity. Such PL intensity behavior is likely due to the Sn nanoislands.

GaSb films were grown by molecular beam epitaxy using AlSb/As/Si transition layers on vicinal Si (001) substrates deflected 6 to the (111) plane. The influence of the GaSb films crystallographic orientation on their structural properties and surface morphology is investigated. It was found that GaSb(001 ̅)/Si films are characterized by better structural perfection, lower concentration of point defects and more planar and isotropic surface topography, compared with GaSb(001) films. Possible reason for the observed differences between GaSb films with different orientations is increased density of antiphase domains in GaSb(001) films. The morphological features of the grown films are caused by the terraces edges basically and by the anisotropy of the incorporation of Ga adatoms into the terraces edges, to a lesser extent.