Papers by Keyword: Stacking Fault

Abstract: We evaluated stacking faults expanding by body diode current stress in the SiC Semi-SJ MOSFET for the first time. It was found that body diode degradation of the SJ MOSFETs tends to be smaller than that of conventional Non-SJ MOSFETs. Detailed crystal evaluations revealed that the stacking faults did not expand into the SJ structure. It is assumed that the expansion stops due to low carrier densities. The result suggests that the SJ device has a high potential as a device for suppressing the body diode degradation.

Abstract: 3C silicon carbide is a semiconductor with remarkable properties, making it ideal for the development of long lasting devices, working in harsh environments and under high particle flows. The most significant obstacle to its wider diffusion is the presence of extended, bidimensional and linear defects in its crystal lattice. The purpose of this research is to automatically recognize defects from a TEM image by algorithm that calculates distances and angles.

Abstract: Epilayers grown on substrates etched by various etching conditions were studied for stacking fault defects. Substrates were etched by H₂, H₂+ HCl and H₂ + C_xH_y gases prior to epilayer growth for comparison. High density of SF was observed in the epilayers when H₂+HCl or H₂+C_xH_y gas mixtures were used. On the other hand, much lower density of stacking faults (SF) (<1 cm^-2) was observed in the epilayer grown on the surface etched by only H₂ gas. However, a high number of pits were generated in the epilayer grown on substrate etched by H₂ only, which can be considered to be tradeoff of achieving low SF in epilayer by substrate etching. We also conclude from our experimental results that C rich surface is more favorable to generate SF in epilayer compared to Si rich surface.

Abstract: Dislocations and stacking faults in 4H-SiC (0001) _si epitaxial wafer was inspected by mirror projection electron microscopy (MPJ) with the aid of low-energy SEM and FIB-STEM. MPJ observation found dislocation conversion near the wafer surface, and the conversion was confirmed by micro etch pit and low energy SEM method. Another conversion occurred in the epitaxial layer on array of TED half loops, which were detected by MPJ, was also observed by cross-sectional STEM.

Abstract: The effect of varying growth rate on the formation of defects in homo-epitaxially grown cubic silicon carbide (3C-SiC) is studied. Three growth rates are considered (30, 60 and 90 μm/hr) demonstrating that as the growth rate increases the density of point defects, as demonstrated by photo- luminescence, and stacking faults (SFs), as measured by a KOH etching procedure, increase. Scanning transmission electron microscopy images demonstrate generation, annihilation and closure of SFs as a function film thickness. High resolution X-ray diffraction is used to uncover the higher quality of homo-epitaxial with respect hetero-epitaxial films through the examination of the sample mosaicity and SF density.

Abstract: To understand the effects of temperature and injection current density on expansion of Shockley stacking faults (SSFs) from basal-plane dislocations in 4H-SiC p-i-n diodes, the threshold current density for SSF expansion was investigated at eight temperatures by electroluminescence image observation. The threshold injection current density was found to decrease at lower temperatures and to increase at higher temperatures. We identified the origin of this temperature dependence and found that the limiting factor for expansion differed depending on the temperature.

Abstract: We have investigated the surface effect of colloidally prepared CdSe nanocrystals (NCs) with the size range of 23-40 Å on their structural properties by changing the organic capping ligands. The TOPO/HDA-passivated NCs reveal a size-dependent behavior involving an elongated axial bond R⁽¹⁾ of an atomic tetrahedron and a shrunken equatorial bonds R⁽²⁾. After treatment of the NCs with pyridine, the bond length R⁽¹⁾ decreases significantly whereas R⁽²⁾ remains unchanged relative to the TOPO/HDA-passivated NCs, suggesting that a tensile stress along the [001] direction is contributed from the surface modification. In addition, we find that the expansion ratio of the pyridine-treated NCs along the c axis depends strongly on the density of stacking faults, which provides an evidence for the relaxation of atomic positions near the interface of stacking faults.

Abstract: A temperature dependence of the tensile mechanical properties, microstructure and fracture mechanism of high-nitrogen Fe-(19-23)Cr-(17-21)Mn-(0-3)V-(0.1-0.3)C-(0.5-0.9)N vanadium-free and vanadium-containing steels was investigated. For all steels, the 0.2% offset yield strength and strain-hardening drastically increase with a decrease in test temperature. This is associated with high interstitial solid solution strengthening of the steels and more pronounced twinning and stacking-fault formation during straining below room temperature. For the vanadium-free steel, a ductile-to-brittle transition was evaluated: at 77K specimens destroy by cleavage mechanism while at room temperature steels show ductile fracture. Vanadium-alloying provides a particle strengthening of the steels and, at the same time, reduce solid-solution strengthening. Increase of vanadium concentration fully or partially suppress brittle fracture of the steels at 77K. Particle strengthening changes interstitial solid-solution effect, dislocation arrangement and slip/twinning relation in vanadium-containing high-nitrogen steels compared to vanadium-free one.

Abstract: We have performed capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements on Schottky contacts fabricated on triangular defects in 4H-SiC epitaxial layers. These measurements are a case study on the effect of a specific extended defect on the DLTS spectrum in order to contribute to the physical understanding of curious features occasionally observed in DLTS spectra. Our measurements reveal an inversion of the DLTS signal depending on applied voltages and filling pulse lengths, and a step in the C-V characteristic of the Schottky diode. We present a model that qualitatively describes the experimentally obtained data. In this model, we assume that stacking faults within a triangular defect form quantum wells, which can capture electrons from other defects during the DLTS measurement leading to the inversion of the DLTS spectrum. Moreover, by calculating the differential capacitance using a self-consistent Schrödinger-Poisson-Solver, the step in the C-V measurements is reproduced by our model.

Abstract: We investigated the expansion of stacking faults (SFs) under a high current pulse stress in detail. In situ observations showed bar-shaped SFs and two types of triangle SFs with different nucleation sites. The calculated partial dislocation velocity of the bar-shaped SFs was four times faster than that of the triangle SFs. The temperature dependence of the partial dislocation velocity was used to estimate activation energies of 0.23±0.02 eV for bar-shaped SFs and 0.27±0.05 eV for triangle SFs. We also compared the electrical characteristics before and after the stress. The forward voltage drop slightly increased by 0.05 V, and the leakage current did not increase.