Solid State Phenomena Vols. 178-179

Abstract: Back–side diffraction gratings enhance a solar cell’s near–band–gap response by diffracting light into higher orders and thereby reducing front–side escape losses. The resulting increased photon absorption and carrier generation improves short–circuit current densities and solar cell efficiencies. Combining rigorous coupled–wave analysis and ray tracing yields a three–dimensional, polarization sensitive optical model to calculate Si absorbance, front–side and back–side losses. For industrially used, pyramidally textured, 180 μm Si solar cells with 85 nm SiN_x anti–reflection coating, the application of an optimized back–side grating enhances the short–circuit current density by ≈ +1 mA/cm², a relative increase of ≈ +2.7 %.

Abstract: Hydrogenated Si nanocrystals were performed by high-dose (51017 cm-2) low-energy (24 keV) H+ ion implantation of silicon-on-insulator (SOI) layers. The formation of the nanocrystalline phase was observed in the as-implanted samples and in those annealed at the temperature of 200-400o C. Both the Raman shift and the broadening of the phonon peak corresponded to Si nanocrystals with the diameters ranging from ~2 to ~3 nm. The room-temperature photoluminescence (PL) peaked at 1.58 - 1.64 eV was observed at room temperature. The PL peak energy corresponded to the energy of quantum confined exciton in the Si nanocrystals with the diameters mentioned above. The PL intensity had the bell-shaped dependence on the measurement temperature and had its maximum near 150 K. The estimated thermal activation energy of the PL was about 12.1 meV and was in good accordance with the singlet-triplet splitting energy of the exciton states.

Abstract: We propose electro-tunable composite structure of microcavity based on silicon 2D photonic crystal bar with a trench defect infiltrated with a liquid crystal. The device is fabricated by joint photo-electrochemical etching of deep macropores and trenches with subsequent trench opening from the substrate side. The optimized geometry and etching regime enables to minimize the lattice distortion introduced by trenches and to reduce roughness of the trench side walls. It was demonstrated that the structures with reach- through trenches and dead-end macropores are suitable for selective filling with a liquid crystal.

Abstract: We have presented a technique, based on magnetron sputtering of silicon target in the mixture of argon, silane, and oxygen. Addition of oxygen gas was shown to cause formation of silicon suboxide layers with amorphous silicon nanoclusters without subsequent annealing. The layers exhibit significant photoluminescence at room temperature. Their photoluminescence spectra reveal special features predicted in the preceding well-known theoretical works. Heterostructures, fabricated with such layers, show high photocurrent efficiency in short-wavelength spectral region. Our results demonstrate that the investigated structures are promising for photoelectric and photovoltaic applications.

Abstract: Over the last few decades convincing evidence has been collected demonstrating that the oxide reliability is most seriously affected by hole trapping into defects. Recently, valuable information has been delivered by a newly developed measurement technique called time-dependent defect spectroscopy (TDDS), which allows to analyze the behavior of single defects. It indicates the existence of additional metastable defect configurations which are necessary to explain various features seen in TDDS. In this study, it will be shown that these bistable defects may also be the origin of noise phenomena, such as temporary and anomalous random telegraph noise observed in MOSFETs.

Abstract: The behavior of the oxygen-containing precipitate in silicon wafer on different stages of the getter formation process is considered from the mechanical point of view. The precipitate is modeled as a spheroidal inclusion undergoing inelastic eigenstrains in an anisotropic silicon matrix. The stress-strain state in the precipitate and matrix is calculated within the framework of the model. An energetic criterion of breaking the spherical shape by the coherent precipitates is obtained and analyzed. Criteria of the formation and onset of motion of the dislocation loops in the vicinity of the precipitate are also proposed. The obtained results are compared with the available experimental data.

Abstract: High angle close to 90° tilt Si boundary created by direct wafer bonding (DWB) using SmartCut® technology is studied in this work. Experimental identification of defects and morphologies at the interface is realized using conventional transmission electron microscopy (TEM) and geometric phase analysis (GPA) of high-resolution TEM images. Atom reconstruction of the interface along the direction is carried out within the frame of the O-lattice theory. We demonstrate that to preserve covalent bonding across the interface it should consist of facets intersected by a maximum of six planes with three 90° Shockley dislocations per facet. For a long enough interface the formation of Frank dislocations is predicted with a period equal 6 times that of Shockley dislocations. Long range undulations of the interface are shown to be related directly to a deviation from exact 90° tilt of the layer with respect to the substrate.

Abstract: We present numerical simulations of nucleation kinetics of vacancies and interstitials during RTA and we study the impact of annealing temperature on bulk micro defect concentration. Since the concentration of vacancies and oxygen and also its diffusion kinetics are significantly different inside Czochralski silicon, we assume the nucleation of vacancies and oxygen independent on each other. We show that different populations of voids formed during RTA can influence formation of oxygen precipitate nuclei. According to classical nucleation theory the homogeneous nucleation dominates around temperatures 500 °C while the calculation of oxygen diffusion into the voids shows that the oxygen clusters over the critical size can be formed above temperatures 700 °C. The nuclei concentration of BMD is thus the superposition of homogeneous nucleation below 700 °C and heterogeneous one prevailing above 700 °C.

Abstract: The numerical modeling of melt flow, heat transfer and impurity (phosphorus) diffusion in the double crucible of "Redmet-90M" Cz puller was carried out in an application to a 200 mm diameter Si single crystal growth. The double crucible consists of two coaxial crucibles having different sizes: 490 mm (external) and 300 mm (internal) inner diameters. The bottom of internal crucible has a central hole of Do = 6 and 12 mm diameter for melt inflow from the external crucible. During crystal pulling the granulated Si was added in the external crucible and a melt of the internal crucible was doped by phosphorus. Three-dimensional features of a rotating melt flow affecting on heat transfer and impurity diffusion in the internal crucible were analyzed. In particular, the melt precession and thermal asymmetry near the liquid-solid interface (LSI) in the internal crucible are discussed. It is shown that a significant phosphorus losses caused by its evaporation from a melt surface may be compensated by additional phosphorus doping in the internal crucible.

Abstract: Lifetime distribution of a multicrystalline silicon ingot of 250 mm diameter and 100 mm height, grown by unidirectional solidification has been modeled. The model computes the combined effect of interstitial iron and dislocation distribution on minority carrier lifetime of the ingot based on Shockley Read Hall (SRH) recombination model for iron point defects and Donolato’s model for recombination on dislocations. The iron distribution model was based on the solid state diffusion of iron from the crucible and coating to the ingot during its solidification and cooling, taking into account segregation of iron to the melt and back diffusion after the end of solidification. Dislocation density distribution is determined from experimental data obtained by PVScan analysis from a vertical cross section slice. Calculated lifetime is fitted to the measured one by fitting parameters relating the recombination strength and the local concentration of iron