Dislocation studies in VCz GaAs by laser scattering tomography

Dislocation cell structures in melt‐grown semiconductor compound crystals

“…2 shows an image of dislocation cells of an as-grown 6" VCz GaAs crystal taken by x-ray synchrotron topography. The dislocations are accumulated in fuzzy walls of certain thickness (50 -100 µm) as was likewise reported elsewhere [9,24,43,44,45]. Typically, numerous junctions and pins form a sessile dislocation jungle (see also refs.…”

“…There are some authors ascribing dislocation cell patterns in semiconductor compounds exclusively to such morphological instable interface [22,23]. However, as we clarified by depth integrating laser scattering tomography (LST) in GaAs [24] the dislocation cells are of globular type that contradicts longitudinal formed ones to be expected at cellular-shaped crystallization front. Moreover, as it is well known, dislocation cells may disappear completely if certain dopants are added, like In to GaAs [25] or Se to CdTe [26] although their presence should even promote constitutional supercooling.…”

“…1c [11,13,24,25,37,38]. The cells are of globular type [24] and their size decreases with increasing average dislocation density [35,37].…”

“…Typically, numerous junctions and pins form a sessile dislocation jungle (see also refs. [24,44]) which is rather stable against post-growth annealing [46,49]. The analysis of the full width at half maximum (FWHM) of the x-ray rocking curve (XRC) over standard GaAs wafers revealed that only very small mean tilt angles around 10 arc sec do exist between the cells [13,47,48].…”

Simulating Interface Growth and Defect Generation in CZT – Simulation State of the Art and Known Gaps

“…In addition, crystal growth under industrial conditions often involves large thermal gradients and thus generates thermal strains and residual stresses during cooling and/or in the final product. These stresses may cause dislocation nucleation and motion, and dislocation network formation [122]. Combining the thermal stress in a cylindrical growing crystal with the basic <110>(111) glide system of the zincblende structure the Schmidt contour can be theoretically calculated [123] and shows that the stress relaxes by radial glide along <110> directions.…”