Study of V and Y Shape Frank-Type Stacking Faults Formation in 4H-SiC Epilayer

Abstract

Nomarski optical microscopic, KOH etching and synchrotron topographic studies are presented of faint needle-like surface morphological features in 4H-SiC homoepitaxial layers. Grazing incidence synchrotron white beam x-ray topographs show V shaped features which transmission topographs reveal to enclose 1/4[0001] Frank-type stacking faults. Some of these V-shaped features have a tail associated with them and are referred to as Y-shaped defects. Geometric analysis of the size and shape of the V-shaped faults indicates that they are fully contained within the epilayer and appear to be nucleated at the substrate/epilayer interface. Detailed analysis shows that the positions of the V-shaped stacking faults match with the positions of c-axis threading dislocations with Burgers vectors of c or c+a in the substrate and thus appear to result from the deflection of these dislocations onto the basal plane during epilayer growth. Similarly, the Y-shaped defects match well with the substrate surface intersections of c-axis threading dislocations with Burgers vectors of c or c+a in the substrate which were deflected onto the basal plane during substrate growth. Based on the observed morphology of these defect configurations we propose a model for their formation mechanism.

X-ray Topography Studies of Relaxation during the Homo-Epitaxy of 4H-SiC

“…The calculated misfit strain required for the creation of an ID at the measured critical thickness of 4.4 μm (measured directly from the SWBXT image in Fig. 6 see [19]) is around 2x 10 -5 , which is comparable to the value extrapolated from Sasaki's work. Thus the misfit strain due to the doping difference between substrate and epilayer is enough to produce IDs when the conditions are favorable.…”

“…1 (a) reveals the presence of pairs of additional linear features which are slightly inclined to the ID segments. The Burgers vector associated with these features is also 1/3 [11][12][13][14][15][16][17][18][19][20]. These features are also clearly visible in Fig.…”

“…These configurations comprise two straight, screw-oriented BPD segments (with Burgers vector along the offcut direction, i.e. 1/3 [11][12][13][14][15][16][17][18][19][20], as determined by their invisibility on the [1-100] reflection, not shown here) in the substrate, connected to two ID segments, which in turn are connected to two mobile segments on the basal plane of the epilayer. The lower ends of the straight, screw oriented segments in the substrate are invariably connected to complex BPD nodes that apparently have provided pinning points.…”

Characterization of V-Shaped Defects Formed during the 4H-SiC Solution Growth by Transmission Electron Microscopy and X-ray Topography Analysis

“…Similar V-shaped contrasts in X-ray topographic images also were reported by other researchers in 4H-SiC CVD growth. It is emphasized that all of these V-shaped defects in the CVD crystal contain stacking faults between two branches of “V”. − In order to characterize the newly discovered V-shaped defects in our case, TEM studies have been conducted using [112̅0] cross-sectional specimens. First, a topographic image was obtained by incidence X-ray topography using 11-28 diffraction.…”

“…Recently, we discovered unidentified defects corresponding to V-shaped contrasts in X-ray topographic images of the crystals grown by 4H-SiC solution growth which may hamper the reduction of dislocations density. Moreover, we made clear that the new V-shaped defects are different from similar V-shaped defects in CVD layers. − In this study, we characterized the newly discovered V-shaped defects peculiar to the solution growth by synchrotron X-ray topography and transmission electron spectroscopy (TEM) observation. To the best of our knowledge, this is the first report on the present type of defects which corresponds to the V-shaped topography contrasts during the 4H-SiC (0001) solution growth.…”