Papers by Keyword: Structural Defects

Abstract: The microstructure of Fe61Co10Zr2,5Hf2,5Nb2W2B20 amorphous alloy in the form of ribbons obtained by classical melt spinning and plates obtained by an induction suction method were investigated using X-ray diffraction. The type of structural defects were studied by analysis of the magnetization characteristics near ferromagnetic saturation of the sample. It was shown that the presence of structural defects is strongly correlated with sample thickness and production process. It was shown that ribbons with cooling rate between 105-106 K/s have point type defects, wires obtained with lower cooling rate between 101-102 K/s, have linear type defect (quasi-dislocation dipoles). crystallization.

Abstract: Thick 4H-SiC epitaxial layers have been characterized using high-resolution lifetime mapping. The lifetime maps are obtain by the detection of photoluminescence decay of the band gap emission. Full wafers mappings with 200 m resolution reveal lifetime variations that can be associated with structural defects replicated from the substrate, and variations in epitaxial growth conditions due to the susceptor design. High resolution mapping over smaller regions with down to 20 m step size, reveals local lifetime reductions associated with different structural defects in the epitaxial layer. Identified defects that influence the lifetime are the carrot defect, different types of in-grown stacking faults, and an unidentified defect associated with a pair of basal plane dislocations on the surface. Also clusters of threading screw dislocations, probably originating from a dissociated micropipe in the substrate, are found to reduce the lifetime.

Abstract: We demonstrated the rapid and nondestructive observation of structural defects in SiC wafers by full-wafer photoluminescence (PL) imaging under below-gap excitation. The use of visible light emitting diode arrays as an excitation source is essential to the simplification of an optical system and the light excitation covering the whole wafer. We were able to observe the defect-related intensity patterns similar to those obtained by conventional laser-scanning PL mapping. The measurement time of the PL imaging was more than fifty times faster than that of the PL mapping.

Abstract: Raman spectroscopy and photoemission microscopy were coupled as two complementary non-destructive optical techniques in order to study biased 4H-SiC pin diodes. These two characterization tools have been largely used for the study of semiconductors but the combination of these two techniques has hardly been reported so far. Some structural defects inducing the same electrical damage could be discriminated and identified. Temperature could be measured in operating devices and the influence of the diode operating mode on the Raman signal could be evidenced.

Abstract: We carried out mapping of the excess carrier lifetime for a bulk p-type 4H-SiC wafer by the microwave photoconductivity decay (μ-PCD) method, and we compared the lifetime map with structural defect distribution. Several small regions with short lifetimes compared with surrounding parts are found, and they correspond to regions with high-density structural defects. Excess carrier decay curves for this wafer show a slow component, which originates from minority carrier traps. From temperature dependence of the excess carrier decay curve, we found decrease of the time constant of the slow component with increasing temperature. We compared the activation energy of the time constant with that obtained from the numerical simulation, and concluded that the energy level for the minority carrier trap would be 125 meV from the conduction band.

Abstract: 4H-SiC pin diodes were fabricated on epitaxial layers grown by Sandwich Sublimation Method (SSM). I-V and photoemission measurements were conducted on these devices. These measurements show hot spots responsible for a soft breakdown and evidence triangular shape defects previously observed in 4H-SiC pin diodes made on CVD epitaxial layers. These results agree with the morphology studies which indicate that the SSM-grown layers have a higher number of structural defects than their counterparts.

Abstract: The advantages and uniqueness of the Inorganic modification of the Sol-Gel method have already been described. Homogeneous nano-composites as well as some exotic glasses, complex-metal-oxides systems with little glass-forming ability, can be produced by this method. Thus, the obtained materials are characterized by a complex structure that leads to the wide variety of physical and chemical properties. Zirconia-containing materials are of utmost interest because of the mechanical toughness and chemical resistance provided by the presence of ZrO2. In the present work, we report on unusual structural peculiarities of the Zr-O, two types of Zr-Ge-O systems (with Zr>Ge and Zr

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