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A number of important but little-investigated problems connected with III-V/Ge heterostructure in the GaInP/GaInAs/Ge multijunction solar cells grown by MOVPE are considered in the paper. The opportunity for successfully applying the combination of reflectance and reflectance anisotropy spectroscopy in situ methods for investigating III-V structure...
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Multijunction solar cells based on III–V compounds are one of the most effective possibilities to achieve high efficiencies for space and terrestrial applications. In this work, AlInAs:C/InP:S tunnel junctions are fabricated using MOVPE. Type-II interface band alignment of AlInAs/InP heterostructure is ideal for increasing the photogenerated carrie...
Citations
... The ternary gallium indium phosphide (GaInP) alloy is widely used in bipolar transistors [1][2][3], in various heterojunction nanostructures [4,5], as well as in efficient single and multijunction solar cells as the largest bandgap top cell [6][7][8]. Moreover, cells based on GaInP 2 lattice-matched with GaAs or Ge substrates are very promising for solar water splitting [9][10][11][12]. ...
... If the experimentally available values of the surface band bending y 0 at different temperatures and the other parameters are known, the density of surface states can be obtain from the solution of the equation (8). In this case, the parameter γ is selected so that the values of the surface potential y 0 (300 K) and y 0 (77 K) coincide with the experimental results. ...
... If these levels occur in the depth of the band gap, the occupation of the surface states will be close to unity. Therefore two different solutions of the equation (8) corresponding to different energy and density of surface states can exist for one value of δ. In this case, for a reasonable estimation of the surface state energy, the additional data on the surface state density is necessary. ...
Surface potentials in chemically etched n- and p-GaInP2(100) are investigated by synchrotron-radiation photoemission spectroscopy at room and liquid-nitrogen temperatures. It is found that at low temperature the surface band bending in both n- and p-GaInP2(100) is
reduced so that the surface bands become nearly flat. This effect is explained in the framework of semiconductor surface electrostatics. The proposed model enables quantitative characterization of the surface state spectrum based on the experimentally determined values of the surface potential at different temperatures. In particular, the surface states density values obtained are 2 × 1012 and 7 × 1012 cm–2 for n- and p-GaInP2(100) surfaces, respectively.
... Multijunction solar cells (Fig. 21d) based on III-V semiconductor heterostructures are widely used in space and ground concentrator photovoltaic systems due to their high efficiency and radiation resistance [370]. In addition, double-junction solar cells are widely used as photocathodes in devices for the photoelectrochemical decomposition of water under sunlight irradiation [371][372][373]. ...
Recent experimental and theoretical data on modification of the atomic and electronic structures of the surface of different III–V semiconductors by electrolyte solutions are reviewed. The interrelation between chemical reactions occurring at semiconductor/electrolyte interfaces, the charge transfer between the semiconductor and the solution, and corresponding modifications of the atomic and electronic structures of the semiconductor surface is established. Examples of modification of the electronic characteristics and properties of semiconductor devices and nanostructures under interaction with electrolyte solutions are given.
... [122] For example, the MOVPE growth of entire laser and MJSC structures can be monitored in situ with RAS. [123,124] For multinary III/V compounds, the choice of a suitable growth regime is more important compared to the rather stable growth of binaries. Often, different growth conditions also relate to different surface structures, which can be observed with RAS. ...
Solar energy conversion and photoinduced bioactive sensors are representing topical scientific fields, where interfaces play a decisive role for efficient applications. The key to specifically tune these interfaces is a precise knowledge of interfacial structures and their formation on the microscopic, preferably atomic scale. Gaining thorough insight into interfacial reactions, however, is particularly challenging in relevant complex chemical environment. This review introduces a spectrum of material systems with corresponding interfaces significant for efficient applications in energy conversion and sensor technologies. It highlights appropriate analysis techniques capable of monitoring critical physicochemical reactions in situ during non-vacuum preparation and photoactivity studies including well-defined inorganic epitaxial reference surfaces, buried interfaces, and low-defect nucleation of disjunct epitaxial materials that are analyzed during preparation in chemical vapor environment. Their surfaces are then modified and functionalized in gaseous and liquid environment. Finally, even more complex coupling of inorganic stable photoactive materials with responsive soft matter for bioactivity is reviewed. Interface formation, structure, and/or artificial photochemical interfacial reactions are scrutinized down to the atomic scale in real time, also accounting for equilibrium versus non-equilibrium, kinetically driven processes, in order to accelerate progresses in the realization of efficient energy materials and in the exploitation of photoinduced processes at interfaces.
... Gallium indium phosphide (GaInP) is a ternary semiconductor compound used in GaAs heterojunction bipolar transistors [1][2][3][4], in a variety of heterojunction nanostructures [5,6], and in efficient single and multijunction solar cells as the largest bandgap top cell [7][8][9][10]. Besides, cells based on GaInP 2 with the bandgap of 1.8-1.9 ...
Sensors to analyse layer structures already during epitaxial growth provide valuable information for developing device structures and for ensuring the reproducibility of run-to-run conditions. Most analytical online tools are applicable to all major growth techniques. Today a variety of probes is routinely integrated into growth systems for monitoring in situ sample temperature, growth rate, layer thickness, composition, strain, and other parameters of the growth process. Sensors measure either the ambient in the vicinity of the growing sample or the sample surface. Ambient analysis comprises mass spectrometry and optical probes; they provide information about the mass transport, the kind and density of species, their temperature, and potential mutual reactions. Surface probes include diffraction techniques and various optical tools. Surface sensitivity for diffraction is achieved by applying grazing-incidence angles, and the diffracted electron and X-ray beams disclose the surface morphology and reconstructions. Optical probes are widely applied in gaseous growth ambient. The selectivity for the surface may strongly be enhanced by taking advantages of symmetry-related surface properties, and several optical probes can resolve the growth of single monolayers. The chapter describes prominent techniques for in situ analysis of epitaxy. After discussing ambient analysis using mass spectrometry and optical spectroscopy, surface probes are considered. Structural analysis by reflection high-energy electron diffraction and by X-ray diffraction is outlined, and optical probes by pyrometry and deflectometry yielding data on temperature and strain are presented. The text then focuses on reflectometry, ellipsometry, and reflectance-difference spectroscopy (reflectance-anisotropy spectroscopy); these techniques provide both chemical and structural information.
Spectral characteristics of the Ga(In)As subcell of triple-junction GaInP/Ga(In)As/Ge solar cells have been experimentally and theoretically studied. It is established that the use of a wide-bandgap “window” layer with optimum thickness (100 nm for Ga0.51In0.49P, 110 nm for Al0.4Ga0.6As, and 115 nm for the Al0.8Ga0.2As) in Ga(In)As subcell allows the response photocurrent to be increased by about 0.5 mA/cm²; the change of material in the rear potential barrier of the GaInP subcell from Al0.53In0.47P to p⁺-Ga0.51In0.49P or AlGaAs allows the short-circuit current of Ga(In)As subcell to be additionally increased by about 0.8 mA/cm²; and the use of a wide-bandgap n⁺⁺-Ga0.51In0.49P layer instead of n⁺⁺-GaAs in the tunnel diode increases the photocurrent by about 1 mA/cm².
The possibility of growing arrays of InxGa1 – xAs nanocrystals on GaAs substrates by ion-beam deposition is experimentally shown. The influence of the ion energy, current density, and deposition time of sputtered materials on the height, lateral size, and density of arrays of InxGa1 – xAs nanocrystals is investigated. The possibilities of changing controllably the deposition parameters of InxGa1 – xAs(GaAs) nanocrystals are analyzed. The technological growth parameters of InGaAs nanofilms on GaAs are determined. The composition, structural quality, and photoluminescence of InxGa1 – xAs nanocrystals and films grown on GaAs are studied.
The effect of growth conditions on the structural perfection of AlInGaAsP/InP thin-film heterostructures is discussed. The key parameters determining the structural perfection and surface quality of thin AlInGaAsP epitaxial films grown on indium-phosphide substrates from the liquid phase in a temperature-gradient field are determined.
Spectral characteristics of the Ge subcell of triple-junction GaInP/GaAs/Ge solar cells have been simulated. It was shown that using a GaInP nucleation layer that creates a shallow diffusion p–n junction in Ge can raise the photogeneration current of the Ge subcell by ~4.5 mA/cm² as compared with the value in the case of a GaAs nucleation layer. The optimal thickness of the GaInP layer (170–180 nm) makes it possible to additionally raise the photocurrent by ~1.5 mA/cm². It was experimentally demonstrated that the photogenerated current of the Ge subcell of GaInP/GaAs/Ge solar cells increases by 3.9 mA/cm² on replacing the GaAs nucleation layer with GaInP and there is an additional gain by 0.9 mA/cm² on using the optimal thickness of the GaInP nucleation layer.
The effect of bismuth on the structural perfection and the luminescent properties of AlxInyGa1–x–yBizSb1–z/GaSb heterostructures has been studied. The optimal parameters of the process of zone recrystallization with temperature gradient at which epitaxial AlInGaBiSb layers have the minimum roughness and high structural perfection have been revealed: temperature gradient 1 ≤ G ≤ 30 K/cm, the liquid zone thickness 60 ≤ l ≤ 100 μm, the temperature range 773 K ≤ T ≤ 873 K, and bismuth concentration 0.3–0.4 mol fraction.
