The effect of optical excitation conditions on the spectral and temporal characteristics of the radiation from two-dimensional photonic crystals based on the structures with self-assembled Ge(Si) nanoislands has been studied. It was shown that one of the main factors effecting the spectral position and shape of photoluminescence lines, as well as the photoluminescence kinetics of photonic crystals with Ge(Si) nanoislands, along with the mode structure of the photonic crystal, are the local heating of the samples and the concentration of nonequilibrium charge carriers created by the absorption of the pumping radiation.

Two-dimensional Si-based photonic crystals with embedded Ge nanoislands were studied. In particular, dependences of the steady-state and time-resolved photoluminescence response on the depth of the air-holes which form the photonic crystal itself were investigated. It was shown that the maximum luminescence intensity was observed not for the fully-etched photonic crystals but for the intermediately etched ones. The possible origin of such a behavior is discussed.

The results of the experimental study and theoretical simulation of the photoluminescence (PL) spectra of strained germanium microbridges with improved heat sink are reported. It was shown that in the structures under study the main contribution to the PL signal of micro-bridges is provided by the radiative transitions from Г-valley to the valence band in the whole considered temperature range (from 80 to 300 K). The influence of interference and self-absorption effects on the shape of the PL spectra of Ge microbridges is discussed. It was demonstrated that Ge microbridges with improved heat sink which was achieved due to the adhesion of the bridges to the underlying layers due to capillary forces are not subjected to the additional stretching as the temperature decreases in contrast to the suspended ones.

Doping of silicon with bismuth leads to additional spin scattering of the conduction electron by the spin-orbit potential introduced by a heavy donor. In this paper, we discuss spin flip scattering influence on the generation of spin currents in silicon with electronic conductivity. Based on the theory of spin pumping and the diffusion model, the values of spin currents and voltages of the ISHE are calculated with varying the type of donor and its concentration and the spin diffusion lengths. Calculations made it possible to find the dependences of the magnitudes of the effects on the parameters of silicon layers doped with bismuth, and to explain the absence of ISHE signals when the silicon layer is doped only with phosphorus or antimony with a concentration of Nd> 1019 cm-3.

AIIIBV/Ge/Si (001), AIIIBV/Ge/SOI (001), and AIIIBV/GaAs (001) heterostructures were formed and investigated. The Ge buffer layer was produced by the "hot wire" technique on a Si substrate (001) for the AIIIBV/Ge/Si structure. In the case of the AIIIBV/Ge/SOI, the Ge buffer layer was grown on the SOI (001) substrate by molecular beam epitaxy via two-stage growth. The growth of AIIIBV layers were performed by metalorganic chemical vapor deposition. It is shown that the Ge/SOI formed via two-stage growth allows the growth of AIIIBV layers that are not inferior in structural and optical quality to those formed on the Ge/Si.

In this work, formation of locally tensile strained Ge structures (micro-bridges) on SOI substrates embedded into microcavities is reported and their optical properties are discussed. The cavity compatible with the shape of the active region was designed in such a way as to provide an effective localization of the electromagnetic field in the active region of the structure, as well as to minimize the strain redistribution due to the cavity formation. Micro-photoluminescence (PL) studies have shown a remarkable enhancement of the PL intensity for the locally strained areas as compared to the initial Ge film. It was shown that the formation of a microcavity leads to a decrease in the maximum strain in the active region of the structure, but provides an overall increase in the PL intensity.

Light-emitting properties of Ge-on-Si(001) layers doped by Sb were studied by stationary and time-resolved photoluminescence (PL) at room temperature. It was obtained that the PL intensity of n-Ge/Si(001) structures is maximized when the doping level is close to the equilibrium solubility of Sb in Ge (~1019 cm-3) which is in accordance with the previously published data. Time-resolved studies of the direct-related PL signal have shown that both the donor density and the growth conditions of doped layer, in particular, the growth temperature influence the PL kinetics. It was obtained that the increase of doping level leads to the decrease of the characteristic carrier lifetime. Moreover, usage of low growth temperatures which is needed to form the doped n-Ge layers also results in shortening of the carrier lifetime as compared with Ge layers grown at high temperatures. It was found that rapid thermal anneal at proper conditions could partially compensate the above mentioned detrimental effects and lead to the increase of both the PL intensity and carrier lifetime.

Investigations of the photoluminescence (PL) response of 2D photonic crystal slabs with embedded Ge(Si) quantum dots are reported. It was shown that it is possible to obtain the large enhancement of the PL intensity from the active medium (Ge(Si) quantum dots) in the wavelength range of 1.2-1.6 mkm. Features of the PL response associated with the interaction with photonic crystal modes located near the Γ point of the Brillouin zone are studied. It was shown that both relatively wide lines associated with the leaky modes of the photonic crystal and rather narrow resonances with the Q factor exceeding 103 could be observed. The latter sharp resonances could be detected in the specific range of the photonic crystal lattice parameters.

In this work formation of locally strained Ge structures on SOI substrates is reported and their optical properties are discussed. Suspended Ge structures were fabricated by optical lithography, plasmachemical and wet chemical etching using the “stress concentration” approach. The fabrication procedure of suspended structures were modified in such a way to provide the mechanical contact between them and the underlying layers so improving the heat dissipation from them. SOI substrates with top Si layer being only 100 nm thick were utilized in such fabrication scheme. The decrease of local heating in such kind of structures was confirmed by the study of micro-Raman scattering depending of scanning laser power. Micro-photoluminescence measurements have shown the remarkable enhancement of the integrated intensity from locally strained areas of a microstructure. It was also shown that structures brought in contact with underlying layers could sustain much higher pumping power densities without fracture as compared to the suspended ones.

Comparative studies of the luminescent properties of Sb doped Ge layers grown on Si (001) and Ge (001) substrates have been carried out. It is shown that in Ge:Sb/Ge(001) layers, in contrast to the Ge:Sb layers grown on silicon, indirect optical transitions make a significant contribution to the photoluminescence signal. This fact is associated with a longer lifetime of charge carriers in homoepitaxial Ge:Sb/Ge structures due to the absence of crystal lattice defects associated with the relaxation of elastic strain. It is shown that the significant increase in the contribution of direct optical transitions to the total photoluminescence signal observed at higher doping levels of Ge:Sb/Ge(001) layers is caused by an increase in the population of electronic states in the Г valley. The luminescent properties of Ge:Sb/Ge(001) and Ge:Sb/Si(001) layers with Sb concentration significantly exceeding its equilibrium solubility are strongly affected by the nonradiative recombination centers, which may be clusters of impurity atoms.

Необходимым условием для развития современной солнечной энергетики является понижение стоимости солнечных элементов (СЭ) на основе кремния при сохранении их высокой эффективности. Одним из путей снижение стоимости СЭ является уменьшение толщины используемых пластин кристаллического Si (c-Si) до толщин 100 мкм и менее. В данной работе представлены результаты исследований возможности использования Ge(Si) самоформирующихся наноостровков для увеличения эффективности СЭ на основе тонкого с-Si за счет текстурирования его поверхности. Для текстурирования поверхности Si использовались полученные методом МПЭ Ge(Si) самоформирующиеся наноостровки, которые выступали в качестве маски для анизотропного травления Si. Подробно методика текстурирования поверхности Si с помощью Ge(Si) наноостровков представлена в [1]. Преимуществом предлагаемого метода текстурирования поверхности СЭ является малая (< 1 мкм) толщина удаляемого при этом слоя Si, которая значительно меньше толщины в 5-10 мкм, удаляемой при стандартно используемой в настоящее время процедуры текстурирования поверхности Si за счет его травления в KOH. Выполненные сравнительные исследования спектральной зависимости коэффициента поглощения в тестовых образцах (без текстурирования) и в пластинах различной толщины с текстурированной поверхностью продемонстрировали, что развитый метод создания микрорельефа на поверхности Si может быть использован для существенного увеличения доли поглощаемого излучения. Это, как следствие, ведет к росту максимально достижимых значений плотностей тока в СЭ, формируемых на тонких текстурированных пластинах c-Si . В работе на Si пластинах различной толщины, с поверхностью, текстурированной с использованием развитой методики, были созданы и исследованы Heterojunction with Intrinsic Thin layer (HIT) СЭ. При формировании HIT СЭ осаждение слоев аморфного Si осуществлялось методом плазмохимического осаждения из газовой фазы. Была выполнена оптимизация основных параметров СЭ от условий роста и параметров структур с Ge(Si) островками, а также от условий формирования текстурированной поверхности. Показано, что фактор заполнения и КПД для HIT СЭ, сформированных на с-Si пластинах с тектурированной поверхностью, значительно выше, чем в СЭ, созданных на исходных c-Si пластинах. Таким образом, продемонстрирована возможность применения Ge(Si) островков для увеличения эффективности СЭ на основе Si, в том числе и на тонких пластинах c-Si, за счет текстурирования их поверхности.

The impact of rapid thermal treatment on electrical and luminescent properties of Ge:Sb/Si(001) layers which have Sb concentration much higher than the equilibrium solubility limit was investigated. Local modifications of such properties throughout the structure’s depth were revealed using precise wet chemical etching. It was obtained that at relatively low annealing temperatures ( 500°С) the changes of electron concentration and photoluminescence response may occur without any remarkable diffusion-related redistribution of dopant atoms. For the relatively high ( 700°С) annealing temperatures the changes of electrical and optical properties after anneal are caused by the significant Sb bulk diffusion and desorption from the sample surface. In particular Sb bulk diffusion leads to the formation of doped regions in the initially undoped areas which further contribute to the resulting structure conductivity and its photoluminescence signal.

AbstractA laser structure comprising metamorphic InGaAsP layer and InGaAs quantum wells on a non-inclined Si(001) substrate with relaxed Ge buffer layer has been grown for the first time by metal-organic vapor phase epitaxy (MOVPE). The optically pumped lasers exhibit stimulated emission at a wavelength of 1.3 μm. At liquid-nitrogen temperature, the threshold power density of pumping at 0.8 μm amounted to 250 kW/cm^2.

AbstractThe formation and properties of locally tensile strained Ge microstructures (“microbridges”) based on Ge layers grown on silicon substrates are investigated. The elastic-strain distribution in suspended Ge microbridges is analyzed theoretically. This analysis indicates that, in order to attain the maximum tensile strain within a microbridge, the accumulation of strain in all corners of the fabricated microstructure has to be minimized. Measurements of the local strain using Raman scattering show significant enhancement of the tensile strain from 0.2–0.25% in the initial Ge film to ~2.4% in the Ge microbridges. A considerable increase in the luminescence intensity and significant modification of its spectrum in the regions of maximum tensile strain in Ge microbridges and in their vicinity as compared to weakly strained regions of the initial Ge film is demonstrated by microphotoluminescence spectroscopy.

AbstractStressed InGaAs/GaAs quantum-well laser structures are grown by gas-phase epitaxy from organometallic compounds on GaAs substrates and artificial Ge/Si substrates based on Si(001) with an epitaxial metamorphic Ge layer. To suppress the relaxation of elastic stresses during the growth of InGaAs quantum wells with a high fraction of In, strain-compensating GaAsP layers are applied. The structural and radiative properties of the samples grown on substrates of various types are compared. Stimulated radiation at wavelengths up to 1.24 μm at 300 K is obtained for structures grown on GaAs substrates and at wavelengths up to 1.1 μm at 77 K, for structures grown on Ge/Si substrates.

AbstractNew data concerning the influence of a probing beam of bismuth ions on the depth resolution in elemental depth profiling by secondary ion mass spectrometry (SIMS) have been obtained on a TOF.SIMS-5 system using the principle of two separate ion beams. It is established that the existing criterion of nondestructive character of the probing beam, on which this principle is based, is insufficient. Additional processes must be taken into account so as to formulate a more adequate criterion. A regime of depth profiling is proposed that allows the depth resolution to be improved at low energies of sputtering ions.

AbstractHybrid laser structures with AlGaInAs quantum wells are grown by metalorganic vapor phase epitaxy on Ge/Si(100) “virtual” substrates using GaAs and InP buffer layers. Stimulated emission is achieved under optical pumping of the prepared samples in the range of 1.3–1.5 μm at liquid-nitrogen temperature. The stimulated-emission threshold is 30–70 kW/cm^2.

Созданы InGaAs/GaAs/AlGaAs лазерные диоды с квантовыми ямами, выращенными методом МОГФЭ на неотклоненной Si (001)-подложке с буферным слоем Ge. Диоды генерируют стимулированное излучение в импульсном режиме при комнатной температуре в спектральном диапазоне 1.09-1.11 мкм. DOI: 10.21883/FTP.2017.11.45105.19

В работе для растворов КОН и HF:H2O2:CH3COOH исследована селективность травления SiGe-структур в зависимости от их состава. Полученные результаты предложено использовать для создания на кремнии субмикронного рельефа поверхности за счет селективного травления структур с самоформирующимися наноостровками Ge(Si). В предлагаемом подходе наноостровки Ge(Si) служат маской для селективного травления Si в водном растворе KOH с добавлением изопропилового спирта, а затем удаляются с поверхности селективным травлением в HF:H2O2:CH3COOH. Экспериментально показано, что подобный подход позволяет создавать на кремнии субмикронный рельеф поверхности, который приводит к существенному уменьшению коэффициента отражения в широком спектральном диапазоне. Полагается, что предлагаемый метод создания рельефа поверхности может быть использован для повышения эффективности тонкопленочных солнечных элементов на основе кристаллического кремния. DOI: 10.21883/FTP.2017.12.45170.33