Nucleation of threading dislocations in sublimation grown silicon carbide

Abstract

The structural defects in sublimation-grown silicon carbide layers have been investigated by transmission electron microscopy, atomic force microscopy, x-ray topography, and KOH etching. Nucleation of two-dimensional islands on damage free surfaces of high quality Lely seeds led to formation of stacking faults at the initial stages of growth. The location and number of stacking faults correlates with threading dislocation density. Also, the growth rate is shown to have a pronounced effect on the threading dislocation densities. Elementary screw dislocation density has been observed to increase from 20 cm−2 to 4×103 cm−2 for growth rates increasing from 0.02 to 1.5 mm/h. Growth on seeds miscut 5° off the c axis resulted in screw dislocation densities almost two orders of magnitude lower than on axis growth. The results are interpreted as due to SiC stacking disorder at the initial stages of growth.

Propagation behavior of threading dislocations during physical vapor transport growth of silicon carbide (SiC) single crystals

“…TSDs tended to form in pairs with opposite Burgers vectors, and these results bear out the pair generation model of screw dislocations by Dudley et al [6]. Sanchez et al [5] also showed pair generation of edge dislocations at the stacking faults nucleated at the initial stage of growth. If partial dislocations encompassing the stacking faults are of the Shockley type, then the resulting threading dislocations would have an edge character.…”

“…Defect formation at the initial stage of PVT growth of SiC has also been deliberately examined by Sanchez et al [5] using TEM, atomic force microscopy (AFM), X-ray topography and defect selective etching. They observed the formation of basal plane stacking faults at the initial stage of growth on the 6H-SiC (0 0 0 1)Si seed crystal, with densities showing a good correlation with the threading dislocation density.…”

Heavily nitrogen-doped 4H-SiC homoepitaxial films grown on porous SiC substrates

“…Generally, molten KOH etching has been used to observe the density and distribution of the defects in the crystals. The origin of the chemically formed etch pits is not only micropipes, but also other kinds of defects, most probably screw dislocations [13].…”

Growth of Silicon Carbide

“…Screw dislocations in the boules originate mainly from SiC seeds and they are preferred nucleation and growth-promoting centers. Threading dislocations can also be generated by plane misalignment during growth, as a consequence of the overgrowth of inclusions on the growth surface [47], or at the boundaries of slightly misoriented grains [48]. Any nonuniformity in temperature in the region of a spiral growth step will result in a change in the speed of advance of the spiral step.…”