X-Ray Topography Of A Single Superscrew Dislocation In 6H-SiC Through All {100} Faces

1996 ◽  
Vol 442 ◽  
Author(s):  
W. M. Vetter ◽  
M. Dudley
Keyword(s):  
Single Crystals ◽  
Semiconductor Devices ◽  
Image Contrast ◽  
Hexagonal Prism ◽  
Burgers Vector ◽  
X Ray ◽  
Stress Components ◽  
Sic Wafer

AbstractMicropipes, the hollow cores of superscrew dislocations that lie along the c-direction in SiC single crystals, are quite deleterious to the performance of semiconductor devices. In the x-ray topography of longitudinal-cut samples of these crystals, topographs in the reflection (006) show dislocation image contrast associated with the superscrew dislocations lying along the c-axis of the crystal, which is also the direction of the dislocations' Burgers vectors. In the (110) reflection, whose g-vector is perpendicular to the c-axis and the dislocations' Burgers vector, there is also an image of the superscrew dislocation formed, albeit weaker than the corresponding image in the (006) reflection. This dislocation image is thought to represent stress components of the superscrew dislocation in directions perpendicular to the c-axis.In order to investigate the origin of these stress components, steps have been carried out to determine whether the dislocation image is anisotropic in all possible reflections where g={110}. To achieve this we have excised a hexagonal prism-shaped sample from a 6H-SiC wafer, 100μm wide, polished along the six {100} crystallographic faces, such that a single micropipe ran along the axis of the sample. This enabled x-ray topographs to be taken through each of these {100} faces

scholarly journals Breakdown Degradation Associated With Elementary Screw Dislocations In 4H-SiC P+N Junction Rectifiers

1997 ◽  
Vol 483 ◽  
Author(s):  
P. G. Neudeck ◽  
W. Huang ◽  
M. Dudley
Keyword(s):  
Video Camera ◽  
Initial Study ◽  
Hollow Core ◽  
Power Devices ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Current Voltage ◽  
The Impact ◽  
Sic Wafer

AbstractIt is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector > 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = Ic with no hollow core) in densities on the order of thousands per cm2, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p+n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p+n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

Deflection of Threading Dislocations with Burgers Vector c/c+a Observed in 4H-SiC PVT–Grown Substrates with Associated Stacking Faults

2012 ◽  
Vol 717-720 ◽  
pp. 347-350 ◽  
Author(s):  
Sha Yan Byrapa ◽  
Fang Zhen Wu ◽  
Huan Huan Wang ◽  
Balaji Raghothamachar ◽  
Gloria Choi ◽  
...  
Keyword(s):  
Detailed Analysis ◽  
Basal Plane ◽  
Stacking Faults ◽  
Image Contrast ◽  
Threading Dislocations ◽  
Burgers Vector ◽  
Calculated Phase ◽  
X Ray ◽  
White Beam ◽  
Contrast Studies

A review is presented of Synchrotron White Beam X-ray Topography (SWBXT) studies of stacking faults observed in PVT-Grown 4H-SiC crystals. A detailed analysis of various interesting phenomena were performed and one such observation is the deflection of threading dislocations with Burgers vector c/c+a onto the basal plane and associated stacking faults. Based on the model involving macrostep overgrowth of surface outcrops of threading dislocations, SWBXT image contrast studies of these stacking faults on different reflections and comparison with calculated phase shits for postulated fault vectors, has revealed faults to be of basically four types: (a) Frank faults; (b) Shockley faults; (c) Combined Shockley + Frank faults with fault vector s+c/2; (d) Combined Shockley + Frank faults with fault vector s+c/4.

Determination of Burgers Vector of Screw Dislocations in 6H-SiC Single Crystals by Synchrotron White Beam X-Ray Topography

1996 ◽  
Vol 437 ◽  
Author(s):  
W. Si ◽  
M. Dudley ◽  
C. Carter ◽  
R. Glass ◽  
V. Tsvetkov
Keyword(s):  
Single Crystals ◽  
Dislocation Core ◽  
Line Defect ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
White Beam ◽  
Lattice Planes ◽  
Vector Magnitude

AbstractIndividual screw dislocations along the [0001] axis in 6H-SiC single crystals have been characterized by means of Synchrotron White Beam X-ray Topography (SWBXT). The magnitude of the Burgers vector was determined from: (1) the diameter of circular diffraction-contrast images of dislocations in back-reflection topographs, (2) the width of bi-modal images associated with screw dislocations in transmission topographs, (3) the magnitude of the tilt of the lattice planes on both sides of dislocation core in projection topographs, and (4) also the magnitude of the tilt of the lattice planes in section topographs. All of the four methods showed reasonable consistency. The sense of the Burgers vector can also be deduced from the abovementioned tilt of the lattice planes. Results revealed that in 6H-SiC a variety of screw dislocations can be found with Burgers vector magnitude ranging from 1c to 7c (c is the lattice constant along [0001] axis). This work demonstrates that SWBXT can be used as a quantitative technique for detailed analyses of line defect configurations.

Röntgentopographische Untersuchungen an CdTe-Einkristallen

1981 ◽  
Vol 157 (3-4) ◽  
Author(s):  
P. Buck ◽  
M. Nagel
Keyword(s):  
Dislocation Density ◽  
Single Crystals ◽  
Vapor Phase ◽  
Burgers Vector ◽  
X Ray

AbstractThe perfection of single crystals of CdTe grown from the vapor phase has been studied by X-ray topography. Results show that the main defects are dislocations with Burgers vector of the [unk] [110] type. Occasionally those of the [unk] [11[unk]] type are observed. The majority of the dislocations are curved and tangled. The dislocation density is about 10

Complex Behavior of Threading Dislocations Observed in PVT-Grown 4H-SiC Single Crystals

2012 ◽  
Vol 717-720 ◽  
pp. 355-358 ◽  
Author(s):  
Masakazu Katsuno ◽  
Tatsuo Fujimoto ◽  
Hirokatsu Yashiro ◽  
Hiroshi Tsuge ◽  
Shinya Sato ◽  
...  
Keyword(s):  
Single Crystals ◽  
Comparative Studies ◽  
Growth Direction ◽  
Threading Dislocations ◽  
Complex Behavior ◽  
Burgers Vector ◽  
X Ray ◽  
Axis Direction ◽  
Straight Line

Structures and propagating behaviors of threading dislocations (TDs) in PVT-grown 4H-SiC single crystals were both investigated using Synchrotron monochromatic X-ray topography. Comparative studies by examining images obtained for the crystals with different diffraction geometries of (0004) and (11-20) of 4H-SiC revealed that a large amount of TDs are likely to be mixed in character, i.e., dislocations with Burgers vector components of both <0004> and <11-20>. Closer observations of topography images has revealed that, although TDs lie largely along the c-axis direction, some of the TDs show quite a complex propagating behavior: not extending in a straight line but meandering along the growth direction.

Zone-axis ALCHEMI for the rapid assessment of site occupancies in garnets

1986 ◽  
Vol 44 ◽  
pp. 706-707
Author(s):  
M.T. Otten ◽  
P.R. Buseck
Keyword(s):  
Single Crystals ◽  
Rapid Assessment ◽  
Site Occupancy ◽  
Zone Axis ◽  
Synthetic Compounds ◽  
X Ray ◽  
Large Group ◽  
Crystallographic Planes

ALCHEMI (Atom Location by CHannelling-Enhanced Microanalysis) is a TEM technique for determining site occupancies in single crystals. The method uses the channelling of incident electrons along specific crystallographic planes. This channelling results in enhanced x-ray emission from the atoms on those planes, thereby providing the required site-occupancy information. ALCHEMI has been applied with success to spinel, olivine and feldspar. For the garnets, which form a large group of important minerals and synthetic compounds, the channelling effect is weaker, and significant results are more difficult to obtain. It was found, however, that the channelling effect is pronounced for low-index zone-axis orientations, yielding a method for assessing site occupancies that is rapid and easy to perform.

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