CHARACTERIZATION OF EXTENDED DEFECTS IN HIGHLY TE-DOPED (111) GASB SINGLE-CRYSTALS GROWN BY THE CZOCHRALSKI TECHNIQUE

For the first time a detailed description of grown-in extended defects in highly Te-doped [111] CZ-grown GaSb single crystals is given. The nature and density of the defects is correlated with the local tellurium concentration. We observed prismatic dislocation loops with {110} and {111} habit planes (perfect or faulted loops) as the predominant defects, extended dislocation clusters consisting of climbed sessile perfect dislocations, and larger, often multi-layered planar defects with displacement fringe contrast (probably Ga2Te3 precipitates) lying in {111} lattice planes. While the prismatic dislocation loops are already generated at a tellurium concentration of 3 X 10(18) cm-3, dislocation clusters and large planar defects first occur at a tellurium concentration of about 1 X 10(19) cm-3. The prismatic loops and the planar defects are exclusively of extrinsic (interstitial) type. Altogether one can establish a far-reaching similarity with the defect population found in highly Te-doped GaAs. The mechanisms which lead to the formation of defects are discussed on the basis of concepts of the known behaviour of point defects in GaAs.