Micropipe absorption mechanism of pore growth at foreign polytype boundaries in SiC crystals

Abstract

Formation of pores at foreign polytype boundaries in bulk SiC crystals is studied by means of synchrotron radiation phase-sensitive radiography, optical and scanning electron microscopies, and color photoluminescence. It is demonstrated that pores are formed through coalescence of micropipes and extend along the polytype boundaries by means of micropipe absorption. A theoretical model is suggested, which describes the micropipe absorption by an elliptic pore nucleated at the boundary of a foreign polytype inclusion. It is shown that depending on the inclusion distortion, the pore can either be a separate micropipe, or grow up to a certain length, or occupy the whole facet of the inclusion.

Characterization of Defects Evolution in Bulk SiC by Synchrotron X-Ray Imaging

“…By effectively accommodating both the dilatation and orientation misfits between FPI and matrix, these pores in early stages can attract additional random full-core dislocations and MPs from neighboring regions (Fig. 4), as earlier described in detail [13]. In such a way, the interface pores can extend along FPI boundaries and accumulate dislocation charge that is the resulting Burgers vector of all the dislocations absorbed by the pore.…”

“…3(a) demonstrates that the groups of pores (marked by black and white arrows) consist of short tube-shaped or slit-like segments. The morphology of such pores was investigated and attributed to the elastic interaction between MPs and boundaries of FPIs, resulting in coalescence of MPs into larger pores elongated along the boundaries [11,13]. FPIs were indeed observed on the same location, as revealed by the yellow PL images [28] of n-type 4H-SiC containing N and B in Fig.…”

“…The MP density in the group 1 reduced in the wafer II compared to I. The attraction of the MPs to the pore was suggested and explained by their absorption to pores [11,13]. We believe that, at the initial stage of growth, the pores are generated by the attraction of MPs by FPIs, followed by MP coalescence [10,11].…”

“…The nucleation of FPIs in the initial stage is suggested as a basis of massive generation of full-core dislocations [26], pores and MPs [10,11,13,31]. The bottom and lateral faces of growing FPIs are possibly the formation sites of interface dislocation structures to accommodate the misfit or misorientation of the matrix and FPI's crystalline lattices.…”

“…High densities of interface dislocations and vacancies thus formed possibly lead to coagulation of vacancies, forming slit-like pores along the FPI boundaries. Another possible mechanism of pore formation is the attraction and agglomeration of MPs at FPI boundaries [10,11,13], for instance, resulting in the majority of pores observed at the boundaries of FPIs (Fig. 3).…”