The results of a study of the real structure, electrical and photovoltaic characteristics of a monolithic solar module of 15 cells, made based on an array of p-n junctions in a Si (111) silicon wafer, are presented. The p-n junctions were formed by the boundaries of through vertical Al-doped (C= (0.95-1.05)×1019 cm-3) Si channels 100 μm wide at a distance of 3 mm. The perfection of the crystal lattice in the channel and near its boundaries has been investigated by X-ray methods: projection topography and high-resolution diffractometry in the transmission and reflection geometry. It is shown that the channel-matrix interface is coherent and there are no misfit dislocations on it. Typical defects in the p-channel are dislocation half-loops, which are located parallel to the surface of the wafer in its near-surface layer. The investigated solar 15-cells module demonstrates an efficiency of 13% at output 7.5 V and 30 mA. These photovoltaic parameters are comparable with the main electrical parameters of the planar analogues, despite the design features of the Si(Al) channels and the presence of structural distortions near the boundaries of the substrate matrix.
Transformation of microstructure of the buried He bubbles of silicon surface layer after He+ low energy plasma immersion ion implantation and subsequent low-thermal annealing were studied by high resolution X-ray diffraction and reflectivity, Rutherford backscattering spectroscopy, transmission electron and atomic force microscopy methods. The ion energies varied in the range 2 – 5 keV at constant exposure ion doses 5×·1017 cm-2. Formation of a three-layer structure (amorphous a-SiOx layer at the surface, amorphous a-Si layer with helium bubbles and buried helium bubbles heavy damaged tensile strained crystalline c-Si layer) that is retained after annealing was observed. Helium-filled bubbles are observed in an as-implanted sample. Evolution of the multilayer structure and the bubbles due to annealing are revealed and comparing with the structural parameters of an as-implanted sample was done. The bubbles are shown to trend into two-model distribution after annealing. The characteristic bubble size is determined to be in a range of 2–20 nm. Large size helium-filled bubbles are located in the amorphous a-Si layer. Small size bubbles are revealed inside the damaged crystalline Si layer. These bubbles are a major source of tensile strain in c-Si layer.
We investigated structural perfection of porous gallium arsenide layers formed in GaAs (001). Different modes of electrochemical etching of n-type GaAs(001) substrates in fluoride-iodide aqueous electrolytes were used to form porous layers. Their structural properties were investigated by high resolution X-ray and synchrotron radiation diffraction and electron microscopy (SEM, TEM) techniques. It was shown that a single current pulse with a high magnitude forms a discontinuous porous layer with a smooth surface. Subsequent etching with a relatively low current density forms a homogeneous porous structure in the depth with approximately 30% porosity. The porous layer thickness can be varied from a few microns to several tens of microns depending on the etching time. The lattice parameter of porous GaAs layers along the surface normal is decreased by a factor of 1.5×10-4 compared to the GaAs substrate. This contraction is related to the formation of vacancy type structural defects as revealed by the measurement of x-ray diffuse scattering.
Electron transport, optical and structure properties of the shallow pseudomorphic quantum wells (QW) GaAs/InGaAs/GaAs are studied by electrophysical, photoluminescence and X-ray double-axes diffractometry methods. It is revealed that insertion of a thin AlAs potential barrier in the center of QW leads to efficient changes of subband structure and mobility. In the case of shallow and narrow quantum wells the observed decrease of mobility is due to appearance of the different scattering mechanism. X-ray diffractometry study is undertaken in order to distinguish whether it is interface roughness scattering from the introduced barrier or another scattering mechanism.
KEYWORDS: Heterojunctions, X-rays, Crystals, Diffraction, Quantum wells, X-ray diffraction, Data modeling, Scattering, Crystallography, Chemical species
A general mathematical approach is realized for simultaneous treatment of several X-ray rocking curves from different crystallographic planes. The corresponding analysis of experimental X-ray rocking curves for (004), (113) and (115) reflections from the single quantum well GaAs-InxGa1-xAs/GaAs(001) heterostructure have been carried out. This approach allows one to restore the depth profiles of the lattice mismatch and mean-square displacements of atoms from regular positions for particular layers as well as to estimate the anisotropy of in-plane and normal-to-plane random atom displacements.
Optical second harmonic generation (SHG) in amorphous Si/SiO2 multiple quantum wells (MQW) is studied by means of SHG spectroscopy, SHG interferometric spectroscopy and X-ray double-axes reflectometry of the MQW samples with the Si quantum well thickness d ranging from 1.00 to 0.25 nm. The electron density profiles obtained from X-ray reflectometry data confirm multilayer structure presence and refine growth data on d values. The observed modification of the SHG spectra upon decreasing d is interpreted using combination of the resonant two-subband approximation for the nonlocal optical response of each quantum well with the generalized transfer-matrix formalism for the description of light propagation across the whole MQW structure. Agreement with the experiment shows that the description of the quadratic optical response of the MQW structure within the model of a nonlocal piecewise-continuous medium remains valid on the sub-nanometer scale.
Structural characteristics of semiconducting heterostructures AlGaAs/GaAs/AlGaAs containing either single quantum well or two quantum wells separated with a thin AlAs layer are estimated by means of the double-crystal X-ray diffractometry. It is found that an additional Si-doping of outer barrier layers results in the formation of abrupt (less than 2 nm) interfaces at quantum wells.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.